<PAGE>
 
                                 UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549
 
                                 _______________
 
 
                                   FORM 10-Q
 



        [X]      QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                            SECURITIES EXCHANGE ACT OF 1934
                                        
                 For the quarterly period ended March 31, 1999
                                        

                                      OR


        [_]      TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE
                        SECURITIES EXCHANGE ACT OF 1934
                                        

         For the transition period from _____________ to _____________
                                        

                    Commission File Number: 0-20725


                             SIEBEL SYSTEMS, INC.
                                        

            (Exact name of registrant as specified in its charter)


                Delaware                           94-3187233
  (State or other jurisdiction of     (I.R.S. Employer Identification No.)
     incorporation or organization)

              

                            1855 South Grant Street
                              San Mateo, CA 94402
          (Address of principal executive offices, including zip code)


                                 (650) 295-5000
              (Registrant's telephone number, including area code)


Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Sections 13 or 15(d) of the Securities Exchange Act of 1934
during the preceding 12 months (or for such shorter period that the registrant
was required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.
                               Yes [X]  No [_]


  The number of shares outstanding of the registrant's common stock, par value
      $.001 per share, as of May 5, 1999, was 91,059,273.
<PAGE>
 
                              SIEBEL SYSTEMS, INC.

                                   FORM 10-Q

                 For the Quarterly Period Ended March 31, 1999

                               Table of Contents

                                        
<TABLE>
<CAPTION>

Part I.  Financial Information                                                                        Page
                                                                                                      ----
        <S>                                                                                         <C>
         Item  1.  Financial Statements

                   a)   Consolidated Balance Sheets
                        as of March 31, 1999 and December 31, 1998                                      3
 
                   b)   Consolidated Statements of Operations
                        for the three months ended March 31, 1999 and 1998                              4
 
                   c)   Consolidated Statements of Cash Flows
                        for the three months ended March 31, 1999 and 1998                              5
 
                   d)   Notes to Consolidated Financial Statements                                      6
 

         Item 2.   Management's Discussion and Analysis of Financial Condition and                     12
                   Results of Operations

         Item 3.   Quantitative and Qualitative Disclosures About Market Risk                          24


Part II. Other Information
 
         Item 1.   Legal Proceedings                                                                   25
 
         Item 2.   Changes in Securities and Use of Proceeds                                           25
 
         Item 6.   Exhibits and Reports on Form 8-K                                                    25
 

Signatures                                                                                             27
</TABLE> 

                                       2
<PAGE>
 
                        Part I.  Financial Information
                         Item 1.  Financial Statements

                             SIEBEL SYSTEMS, INC.

                          Consolidated Balance Sheets
                     (in thousands, except per share data)


<TABLE>
<CAPTION>
                                                                                             March 31,         December 31,
                                                                                               1999                1998
                                                                                         ----------------    ---------------
                                                                                            (unaudited)

<S>                                                                                 <C>                     <C>
Assets

Current assets:
   Cash and cash equivalents.................................................                 $84,708                $79,961
   Short-term investments....................................................                 145,756                151,888
   Accounts receivable, net..................................................                 147,676                122,818
   Deferred income taxes.....................................................                  13,120                 13,120
   Prepaids and other........................................................                  14,076                 13,908
                                                                                  -------------------     ------------------
     Total current assets....................................................                 405,336                381,695
Property and equipment, net..................................................                  48,328                 45,537
Other assets.................................................................                  14,648                 14,714
                                                                                  -------------------     ------------------
     Total assets............................................................                $468,312               $441,946
                                                                                  ===================     ==================
Liabilities and Stockholders' Equity

Current liabilities:
   Accounts payable..........................................................                 $11,975                 $3,899
   Accrued expenses..........................................................                  66,573                 84,917
   Income taxes payable......................................................                   5,511                 10,917
   Deferred revenue..........................................................                  52,507                 50,875
                                                                                  -------------------     ------------------
     Total current liabilities...............................................                 136,566                150,608
Deferred income taxes........................................................                     642                    710
                                                                                  -------------------     ------------------
     Total liabilities.......................................................                 137,208                151,318
                                                                                  -------------------     ------------------
Stockholders' equity:
  Common stock; $0.001 par value; 300,000 shares authorized; 90,684 and
   89,630 shares issued and outstanding, respectively........................                      91                     90
  Additional paid-in capital.................................................                 254,471                235,302
  Notes receivable from stockholders.........................................                    (406)                 (406)
  Deferred compensation......................................................                    (317)                 (360)
  Accumulated other comprehensive losses.....................................                    (746)                 (669)
  Retained earnings..........................................................                  78,011                 56,671
                                                                                  -------------------     ------------------
     Total stockholders' equity..............................................                 331,104                290,628
                                                                                  -------------------     ------------------
     Total liabilities and stockholders' equity..............................                $468,312               $441,946
                                                                                  ===================     ==================
</TABLE>


          See accompanying notes to consolidated financial statements.

                                       3
<PAGE>
 
                             SIEBEL SYSTEMS, INC.
                                        
                     Consolidated Statements of Operations
               (in thousands, except per share data; unaudited)


<TABLE>
<CAPTION>
 
                                                                         Three Months Ended
                                                                              March 31,
                                                                        1999            1998
                                                                   -------------    -------------
<S>                                                               <C>                <C>

Revenues:

       Software.............................................           $93,432           $56,002
       Professional services, maintenance and other.........            40,618            18,170
                                                               ---------------   ---------------  
                 Total revenues.............................           134,050            74,172          
                                                               ---------------   ---------------        
Cost of revenues:                                                                          
       Software.............................................             1,331             1,016        
       Professional services, maintenance and other.........            24,186            10,805               
                                                               ---------------   ---------------      
                 Total cost of  revenues....................            25,517            11,821            
                                                               ---------------   ---------------      
                 Gross margin...............................           108,533            62,351               
                                                               ---------------   ---------------        
                                                                                                
Operating expenses:                                                                        
       Product development..................................            16,678             8,756     
       Sales and marketing..................................            52,168            35,352     
       General and administrative...........................             8,210             4,567              
                                                               ---------------   ---------------      
                  Total operating expenses..................            77,056            48,675               
                                                               ---------------   ---------------      
                  Operating income..........................            31,477            13,676       
                                                                                                    
Other income, net...........................................             2,395             1,592               
                                                               ---------------   ---------------      
                   Income before income taxes...............            33,872            15,268        
                                                                                                    
Income taxes................................................            12,532             5,520               
                                                               ---------------   ---------------      
                   Net income...............................           $21,340            $9,748          
                                                               ===============   ===============      
                                                                                                
Diluted net income per share................................             $0.20             $0.10            
                                                               ===============   ===============        
Shares used in diluted net income per share                                                  
       computation..........................................           106,761            99,287               
                                                               ===============   ===============      
Basic net income per share..................................             $0.24             $0.11              
                                                               ===============   ===============        
Shares used in basic net income per share                                                    
                                                                        90,214            86,285               
       computation..........................................   ===============   ===============   

Comprehensive income:                                                                     
         Net income......................................            $21,340              $9,748    
                                                                                                    
Other comprehensive income (loss), net of tax:                                                      
        Foreign currency translation adjustments.........                 40                 (17)   
        Unrealized losses on securities..................               (117)                 --      
                                                             ---------------      --------------        
                                                                                                    
Other comprehensive loss.................................                (77)                (17)           
                                                             ---------------      --------------        
               Total comprehensive income................            $21,263              $9,731
                                                             ===============      ==============
                                                                 
</TABLE>



          See accompanying notes to consolidated financial statements.

                                       4
<PAGE>
 
                             SIEBEL SYSTEMS, INC.

                     Consolidated Statements of Cash Flows
                           (in thousands; unaudited)


<TABLE>
<CAPTION>
    
                                                                                        Three Months Ended
                                                                                             March 31,
                                                                                 -----------------------------------
                                                                                        1999              1998
                                                                                 -----------------    ---------------

<S>                                                                      <C>                      <C>

Cash flows from operating activities:                              
       Net income..................................................                 $21,340                  $9,748
       Adjustments to reconcile net income to net cash provided by
       (used in) operating activities:
                 Compensation related to stock options.............                      43                      75
                 Depreciation and amortization.....................                   4,574                   2,572
                 Deferred income taxes.............................                     (68)                 (1,702)
                 Loss on disposal of property and equipment........                      --                     223
                 Provision for doubtful accounts and returns.......                    1,331                    754

                 Changes in operating assets and liabilities:                                                
                     Accounts receivable...........................                 (26,189)                 (7,328)
                     Prepaids and other............................                    (168)                    896
                     Accounts payable..............................                   8,076                   1,606
                     Accrued expenses..............................                 (18,344)                 (1,287)
                     Income taxes payable..........................                   2,467                   4,636
                     Deferred revenue..............................                   1,632                   4,157
                                                                       --------------------     -------------------
                       Net cash provided by (used in)
                        operating activities.......................                  (5,306)                 14,350
                                                                       --------------------      -------------------
Cash flows from investing activities:
       Purchases of property and equipment.........................                  (7,365)                 (4,932)
       Purchases of short-term investments.........................                 (32,153)                (25,217)
       Sales and maturities of short-term investments..............                  38,285                  29,273
       Other assets................................................                      66                   1,482
                                                                       --------------------     -------------------
                       Net cash provided by (used in)
                        investing activities.......................                  (1,167)                    606
                                                                       --------------------     -------------------
Cash flows from financing activities:
       Proceeds from issuance of common stock......................                  11,220                   3,695
                                                                             --------------     -------------------
                       Net cash provided by
                        financing activities.......................                  11,220                   3,695
                                                                       --------------------     -------------------
Change in cash and cash equivalents................................                   4,747                  18,651
Adjustment to conform acquired company's year end..................                      --                  (4,140)
Cash and cash equivalents, beginning of period.....................                  79,961                  70,202
                                                                       --------------------     -------------------
Cash and cash equivalents, end of period...........................                 $84,708                 $84,713
                                                                       ====================     ===================
Supplemental disclosures of cash flow information:
 
 Cash paid for income taxes........................................                 $10,066                    $971
                                                                       ====================     ===================
 Tax benefit from exercise of stock options........................                  $7,873                  $2,520
                                                                       ====================     ===================
                                                                                                                     
</TABLE>


         See accompanying notes to consolidated financial statements.

                                       5
<PAGE>
 
                             SIEBEL SYSTEMS, INC.
                  NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                  (unaudited)
                                        

1. Summary of Significant Accounting Policies

   The accompanying unaudited consolidated financial statements have been
prepared on substantially the same basis as the audited consolidated financial
statements, and in the opinion of management include all adjustments, consisting
only of normal recurring adjustments, necessary for their fair presentation.
The interim results presented are not necessarily indicative of results for any
subsequent quarter or for the year ending December 31, 1999.

   In May 1998, Siebel acquired Scopus Technology, Inc. ("Scopus") in a merger
transaction accounted for as a pooling of interests. Accordingly, all financial
information has been restated to reflect the combined operations of the two
companies. See Note 2.

Principles of Consolidation

   The accompanying consolidated financial statements include the accounts of
the Company and its wholly owned subsidiaries. All intercompany accounts and
transactions have been eliminated.

Revenue Recognition

   Prior to January 1, 1998, the Company recognized revenue in accordance with
Statement of Position ("SOP") No. 91-1, "Software Revenue Recognition." Software
license revenue was recognized when all of the following criteria had been met:
there was an executed license agreement, software had been shipped to the
customer, no significant vendor obligations remained, the license fee was fixed
and payable within twelve months and collection was deemed probable.

   On January 1, 1998, the Company adopted the provisions of SOP No. 97-2
"Software Revenue Recognition."  Revenue is recognized under SOP No. 97-2 when
persuasive evidence of an arrangement exists and delivery has occurred, provided
the fee is fixed and determinable, collectibility is probable and the
arrangement does not require significant customization of the software.  Under
SOP No. 97-2, revenue on multiple element arrangements is allocated to the
various elements based on fair values specific to the Company.

   Professional services, maintenance and other revenues relate primarily to
consulting services, maintenance and training. Maintenance revenues are
recognized ratably over the term of the maintenance contract, typically 12
months. Consulting and training revenues are recognized as the services are
performed and are usually on a time and materials basis.  Such services
primarily consist of implementation services related to the installation of the
Company's products and do not include significant customization to, or
development of, the underlying software code.









                                       6
<PAGE>
 
Cost of Revenues

   Cost of software consists primarily of media, product packaging,
documentation and other production costs, and third-party royalties.

   Cost of professional services, maintenance and other consists primarily of
salaries, benefits and allocated overhead costs related to consulting, training
and customer support personnel, including cost of services provided by third
party consultants engaged by the Company.

Use of Estimates

   The preparation of consolidated financial statements in conformity with
generally accepted accounting principles requires management to make estimates
and assumptions that affect the reported amounts of assets and liabilities and
disclosure of contingent assets and liabilities at the date of the consolidated
financial statements and the reported amounts of revenues and expenses during
the reporting period. Actual results could differ from those estimates.

Cash and Cash Equivalents, and Short-Term Investments

   The Company considers all highly liquid investments with a remaining maturity
of 90 days or less at the date of purchase to be cash equivalents.  Short-term
investments generally consist of highly liquid municipal securities with
remaining maturities in excess of 90 days.  The Company has classified its
short-term investments as "available for sale."  Such investments are carried at
fair value with unrealized gains and losses reported within accumulated other
comprehensive income.  Realized gains and losses on available for sale
securities are computed using the specific identification method.

Property and Equipment

   Property and equipment are stated at cost less accumulated depreciation and
amortization. Depreciation is calculated using the straight-line method over the
estimated useful lives of the respective assets, generally three to five years.
Leasehold improvements are amortized over the lesser of the lease term or the
estimated useful lives of the improvements, generally seven years.

Software Development Costs

   Software development costs associated with new products and enhancements to
existing software products are expensed as incurred until technological
feasibility in the form of a working model has been established. To date, the
time period between the establishment of technological feasibility and
completion of software development has been short, and no significant
development costs have been incurred during that period.  Accordingly, the
Company has not capitalized any software development costs to date.

Intangible Assets

   Included in other assets are various intangible assets, primarily goodwill
related to acquisitions.  These amounts are being amortized over a three-year
period using the straight-line method.  Gross intangible assets were $7,162,000
at March 31, 1999 and December 31, 1998 and the related accumulated amortization
was $1,397,000 and $800,000 at March 31, 1999 and December 31, 1998,
respectively

Advertising

   Advertising costs are expensed as incurred. Advertising expense is included
in sales and marketing expense and amounted to $7,570,000 and $2,304,000 for the
three months ended March 31, 1999 and 1998, respectively.

                                       7
<PAGE>
 
Income Taxes

   The Company uses the asset and liability method of accounting for income
taxes.  Deferred tax assets and liabilities are recognized for the estimated
future tax consequences attributable to differences between the consolidated
financial statement carrying amounts of existing assets and liabilities and
their respective tax bases. Deferred tax assets are recognized for deductible
temporary differences, net operating loss carryforwards and credit carryforwards
if it is more likely than not that the tax benefits will be realized. To the
extent a deferred tax asset cannot be recognized under the preceding criteria,
allowances must be established. Deferred tax assets and liabilities are measured
using enacted tax rates in effect for the year in which those temporary
differences are expected to be recovered or settled.

Net Income Per Share

   Basic earnings per share is computed using the weighted average number of
shares of common stock outstanding. Diluted earnings per share is computed using
the weighted average number of shares of common stock and, when dilutive, common
equivalent shares from options to purchase common stock and warrants outstanding
using the treasury stock method.

Employee Stock Option and Purchase Plans

   The Company accounts for its stock-based compensation plans using the
intrinsic value method. As such, compensation expense is recorded on the date of
grant if the current market price of the underlying stock exceeds the exercise
price.

Foreign Currency Translation

   The Company considers the functional currency of its foreign subsidiaries to
be the local currency, and accordingly, they are translated into U.S. dollars
using exchange rates in effect at period end for assets and liabilities and
average exchange rates during each reporting period for the results of
operations. Adjustments resulting from translation of foreign subsidiary
financial statements are reported within accumulated other comprehensive income.

   The Company utilizes foreign currency forward contracts to hedge its exchange
risk on foreign currency receivable and intercompany balances.  While these
forward contracts are subject to fluctuations in value, which are recorded in
current results of operations, such fluctuations are generally offset by the
changes in value of the underlying exposures being hedged.  The Company does not
hold or issue financial instruments for speculative or trading purposes.

Concentrations of Credit Risk

   Financial instruments that potentially subject the Company to a concentration
of credit risk principally consist of trade accounts receivable. The Company
performs ongoing credit evaluations of its customers and generally does not
require collateral on accounts receivable, as the majority of the Company's
customers are large, well established companies. The Company maintains reserves
for potential credit losses, but historically has not experienced any
significant losses related to any particular industry or geographic area since
the Company's business is not concentrated on any one particular customer or
customer base.  No single customer accounts for more than 10% of revenues; and
the Company's largest customer base, telecommunications, which accounted for
approximately 31% of revenues during the quarter ended March 31, 1999, is
sufficiently broad that the Company does not consider itself significantly
exposed to concentrations of credit risk.

Fair Value of Financial Instruments

   The carrying amount of the Company's cash and cash equivalents, short-term
investments, accounts receivable, and accounts payable approximate their
respective fair values.  Changes in the fair value of the Company's derivative
financial instruments (foreign currency forward contracts) are generally offset
by changes in the value of the underlying exposures being hedged.  The fair
value of the Company's derivative financial instruments at March 31, 1999 was a

                                       8
<PAGE>
 
loss of approximately $81,000.

Impairment of Long-Lived Assets

   The Company evaluates long-lived assets, including goodwill, for impairment
whenever events or changes in circumstances indicate that the carrying value of
an asset may not be recoverable based on expected undiscounted cash flows
attributable to that asset.  The amount of any impairment is measured as the
difference between the carrying value and the fair value of the impaired asset.
The Company does not have any long-lived assets it considers to be impaired.

Comprehensive Income

   In 1998, the Company adopted Statement of Financial Accounting Standard
("SFAS") No. 130, "Reporting Comprehensive Income". This statement establishes
rules for the reporting of comprehensive income and its components.  The
Company's comprehensive income includes net income, foreign currency translation
adjustments and unrealized gains on short-term investments and is presented in
the Consolidated Statement of Operations.  The adoption of SFAS No. 130 had no
impact on total stockholders' equity.  Prior year financial statements have been
reclassified to conform to the SFAS No. 130 requirements.

Recent Accounting Pronouncements

   In June 1998, the Financial Accounting Standards Board issued SFAS No. 133
"Accounting for Derivative Instruments and Hedging Activities".  SFAS No. 133
establishes accounting and reporting standards for derivative instruments,
including certain derivative instruments embedded in other contracts,
(collectively referred to as derivatives) and for hedging activities.  It
requires that an entity recognize all derivatives as either assets or
liabilities in the statement of financial position and measure those instruments
at fair value.  If certain conditions are met, a derivative may be specifically
designated and accounted for as (a) a hedge of the exposure to changes in the
fair value of a recognized asset or liability or an unrecognized firm
commitment, (b) a hedge of the exposure to variable cash flows of a forecasted
transaction, or (c) a hedge of the foreign currency exposure of a net investment
in a foreign operation, an unrecognized firm commitment, an available-for-sale
security, or a foreign-currency-denominated forecasted transaction.  For a
derivative not designated as a hedging instrument, changes in the fair value of
the derivative are recognized in earnings in the period of change.  This
statement will be effective for all annual and interim periods beginning after
June 15, 1999.  Management does not believe the adoption of SFAS No. 133 will
have a material effect on the Company's consolidated financial position or
results of operations.

   In December 1998, the Accounting Standards Executive Committee (AcSEC) of the
AICPA issued SOP 98-9, "Software Revenue Recognition with Respect to Certain
Arrangements", which requires recognition of revenue using the "residual method"
in a multiple element arrangement when fair value does not exist for one or more
of the undelivered elements in the arrangement.  Under the "residual method",
the total fair value of the undelivered elements is deferred and subsequently
recognized in accordance with SOP 97-2.  Management does not believe the
adoption of SOP 98-9 will have a material effect on the Company's consolidated
financial position or results of operations.


2. Scopus Merger

   In May, 1998, the Company completed the acquisition of Scopus, a leading
provider of customer service, field service, and call center software solutions.
Under the terms of the agreement, each outstanding share of Scopus common stock
was exchanged for newly issued shares of common stock of the Company. This
resulted in the issuance of approximately 15.1 million additional shares of the
Company's Common Stock. In addition, all outstanding stock options of Scopus
were converted into the right to acquire the Company's Common Stock at the same
exchange ratio with a corresponding adjustment to the exercise price. In
connection with the merger, the Company incurred direct merger-related expenses
of approximately $13,500,000 consisting of direct transaction fees for
investment bankers, attorneys, accountants and other professional fees of
$9,100,000, integration charges related to duplicate facilities and equipment of
$3,100,000 and other miscellaneous expenses of $1,300,000.  The Company also
incurred indirect merger-related expenses of approximately $1,800,000 for joint
sales training and merger-related marketing costs, which 

                                       9
<PAGE>
 
are included within sales and marketing expenses. At March 31, 1999, accrued 
liabilities included approximately $1,325,000 of unpaid merger-related 
expenses.

   The transaction has been accounted for as a pooling of interests.
Accordingly, the financial statements of Siebel have been restated to include
the financial position and results of operations of Scopus for all periods
presented. Prior to the merger with Siebel, Scopus ended its fiscal year on
March 31. The restated financial statements as of December 31, 1997, and for
prior periods, include Siebel's results of operations for those periods and
Scopus' results of operations for the fiscal period ending three months later.
Beginning January 1, 1998, the reporting periods of Siebel and Scopus were
conformed, and results of operations were combined for the calendar periods
presented.

   The results of operations for the separate companies and the combined amounts
presented in the consolidated financial statements follow:


 
                 (in thousands, unaudited)            Three months
                                                          ended
                                                        March 31,
                                                          1998
                                                    ---------------
                    Total revenues:                         $47,100 
                       Siebel                                27,072          
                       Scopus                       ---------------
                                                            $74,172
                                                    ===============
                    Net income: 
                       Siebel                                $8,284
                       Scopus                                 1,464         
                                                    ---------------
                                                             $9,748
                                                    ===============


3. Net Income Per Share 

   The following is a reconciliation of the number of shares used in the basic
and diluted earnings per share computations for the periods presented:


 
          (in thousands, unaudited)               Three months ended
                                                       March 31,
                                            -----------------------------
                                                  1999             1998
                                            --------------   ------------

Shares used in basic net income per share
 computation                                       90,214          86,285
Effect of dilutive potential common shares         16,547          13,002
                                            --------------   ------------
Shares used in diluted net income per share
 computation                                      106,761          99,287
                                            ==============   ============    

   The Company excludes potentially dilutive securities from its diluted net
income per share computation when either the exercise price of the securities
exceeds the average fair value of the Company's common stock or the Company
reported net losses because their effect would be anti-dilutive.  For the three
months ended March 31, 1999 and 1998, the Company excluded 16,380 and 847,980
employee stock options, respectively, with a weighted average exercise price of
$51.50 and $26.88 per share, respectively, from the earnings per share
computation as their exercise prices exceeded the fair value of the Company's
common stock and, accordingly, their inclusion would have been anti-dilutive.

                                       10
<PAGE>
 
4. Segment and Geographic Information

   The Company and its subsidiaries are principally engaged in the design,
development, marketing and support of Siebel Enterprise Applications, its family
of proprietary software applications.  Substantially all revenues result from
the licensing of the Company's software products and related consulting and
customer support (maintenance) services.  The Company's chief operating decision
maker reviews financial information presented on a consolidated basis,
accompanied by disaggregated information about revenues by geographic region for
purposes of making operating decisions and assessing financial performance.
Accordingly, the Company considers itself to be in a single industry segment,
specifically the license, implementation and support of its software
applications.

                                       11
<PAGE>
 
   Item 2.   Management's Discussion and Analysis of Financial Condition and
             Results of Operations

   The statements contained in this Quarterly Report on Form 10-Q (the "Report")
that are not historical are forward-looking statements within the meaning of
Section 27A of the Securities Act of 1933, as amended (the "Securities Act") and
Section 21E of the Securities Exchange Act of 1934, as amended (the "Exchange
Act"), including statements regarding the Company's expectations, beliefs,
intentions or strategies regarding the future. Forward-looking statements
include, without limitation, statements regarding the extent and timing of
future revenues and expenses and customer demand, statements regarding the
deployment of the Company's products, and statements regarding reliance on third
parties. All forward-looking statements included in this document are based on
information available to the Company as of the date hereof, and the Company
assumes no obligation to update any such forward-looking statement. It is
important to note that the Company's actual results could differ materially from
those in such forward-looking statements.


Overview


   Siebel Systems, Inc. ("Siebel" or the "Company") is the market leader in
enterprise-class sales, marketing and customer service information systems for
organizations focused on increasing sales, marketing and customer service
effectiveness in field sales, customer service, telesales, telemarketing, call
centers, and third-party resellers.  The Company designs, develops, markets, and
supports Siebel Enterprise Applications, a leading web-based application
software product family designed to meet the sales, marketing and customer
service information system requirements of even the largest multi-national
organizations.

   In today's increasingly competitive global markets, businesses must
continuously improve their operations. Having spent considerable effort and
resources in previous years automating finance, manufacturing, distribution,
human resources management, and general office operations, many businesses are
now looking to apply the leverage of information technology to their sales,
marketing and customer service processes. Unlike previous automation efforts
which have focused on decreasing expenses, sales, marketing and customer service
information systems focus primarily on increasing revenues.

   The Siebel Enterprise Applications are comprised of a broad range of advanced
client/server application products designed to allow corporations to deploy
comprehensive customer information systems, product information systems,
competitive information systems, and decision support systems on a global basis.
The Company's products provide support for multiple languages and multiple
currencies with support for a number of frequently interdependent distribution
channels, including direct field sales, telesales, telemarketing, distribution,
retail and Internet-based selling and support.

Results of Operations

Revenues


   Software.  License revenues increased to $93,432,000 for the three months
ended March 31, 1999 from $56,002,000 for the three months ended March 31, 1998
and decreased as a percentage of total revenues to 70% in the first quarter 1999
from 76% in the first quarter 1998.  License revenues increased in absolute
dollars during this period as compared to the respective prior period due to an
increase in the number of licenses of Siebel applications sold to new and
existing customers and also due to licenses of new modules, released with the
latest version of Siebel applications, sold to existing users of Siebel base
applications.  The increase in the number of licenses was primarily due to
continued demand by new and existing customers for products in the Siebel
applications family both in the United States and internationally.  The Company
expects that license revenues will continue to grow in absolute dollars, but
will remain the same or decrease as a percentage of total revenues as the
Company's maintenance revenues continue to grow as a result of increases in the
installed base of customers on maintenance.

   Professional Services, Maintenance and Other. Professional services,
maintenance and other revenues increased to $40,618,000 for the three months
ended March 31, 1999 from $18,170,000 for the three months ended March 31, 

                                       12
<PAGE>
 
1998 and increased as a percentage of total revenues to 30% in the first quarter
1999 from 24% in the first quarter 1998. The increase in the absolute dollar
amount was due to growth in the Company's consulting business and growth in the
installed base of customers with a maintenance component and maintenance
renewals from products licenses in prior periods. First-year maintenance is
typically sold with the related software license. Revenue related to such
maintenance is deferred based on vendor-specific objective evidence of fair
value and amortized over the term of the maintenance contract, typically 12
months. The Company expects that professional services, maintenance and other
revenues will remain the same or increase as a percentage of total revenues due
to increased maintenance revenues derived from the Company's growing installed
base and due to the Company's expansion of its consulting organization to meet
anticipated customer demands in connection with product implementation.

   The Company markets its products in the United States through its direct
sales force and internationally through its sales force and distributors
primarily in Japan, Latin America, South Africa and Asia. International revenues
accounted for 30% and 27% of license revenues for the three months ended March
31, 1999 and 1998, respectively. The Company is increasing its international
sales force and is seeking to establish distribution relationships with
appropriate strategic partners and expects international revenues will continue
to account for a substantial portion of total revenues in the future.

Cost of Revenues

   Software.  Cost of software license revenues includes third party software
royalties, product packaging, documentation and production. Cost of license
revenues increased to $1,331,000 for the three months ended March 31, 1999 from
$1,016,000 for the three months ended March 31, 1998 and as a percentage of
total revenues was 1% for each of the three months ended March 31, 1999 and
1998.  All costs incurred in the research and development of software products
and enhancements to existing products have been expensed as incurred, and, as a
result, cost of license revenues includes no amortization of capitalized
software development costs.  These costs are expected to remain the same or
increase as a percentage of total revenues.

   Professional Services, Maintenance and Other.  Cost of professional services,
maintenance and other revenues consists primarily of personnel, facilities and
systems costs incurred in providing customer support.  Cost of professional
services, maintenance and other revenues increased to $24,186,000 for the three
months ended March 31, 1999 from $10,805,000 for the three months ended March
31, 1998 and increased as a percentage of total revenues to 18% in the first
quarter 1999 from 15% in the first quarter 1998.  The increase in the absolute
dollar amount reflects the effect of fixed costs resulting from the Company's
expansion of its maintenance and support organization and growth in the
Company's consulting business.  The Company expects that professional services,
maintenance and other costs will continue to increase in absolute dollar amount
as the Company expands both its customer support organization to support a
growing installed base and its consulting organization to meet anticipated
customer demands in connection with product implementation.  These costs are
expected to remain the same or increase as a percentage of total revenues.

Operating Expenses

   Product Development. Product development expenses include expenses associated
with the development of new products, enhancements of existing products and
quality assurance activities, and consist primarily of employee salaries,
benefits, consulting costs and the cost of software development tools. Product
development expenses increased to $16,678,000 for the three months ended March
31, 1999 from $8,756,000 for the three months ended March 31, 1998 and as a
percentage of total revenues was 12% for each of the three months ended March
31, 1999 and 1998. The increase in the absolute dollar amount of product
development expenses was primarily attributable to costs of additional personnel
in the Company's product development operations. The Company anticipates that it
will continue to devote substantial resources to product development. The
Company expects product development expenses to increase in absolute dollar
amount but remain at a similar percentage of total revenues as in the first
three months of 1999. The Company considers technological feasibility of its
software products to have been reached upon completion of a working model that
has met certain performance criteria. The period between achievement of
technological feasibility and general release of a software product is typically
very short, and development costs incurred during that 

                                       13
<PAGE>
 
period have not been material. Accordingly, the Company has not capitalized any
software development costs to date.

   Sales and Marketing.  Sales and marketing expenses consist primarily of
salaries, commissions and bonuses earned by sales and marketing personnel, field
office expenses, travel and entertainment and promotional expenses. Sales and
marketing expenses increased to $52,168,000 for the three months ended March 31,
1999 from $35,352,000 for the three months ended March 31, 1998 and decreased as
a percentage of total revenues to 39% in the first quarter 1999 from 48% in the
first quarter 1998.  The increase in the dollar amount of sales and marketing
expenses reflects primarily the hiring of additional sales and marketing
personnel and costs associated with expanded promotional activities.  The
Company expects that sales and marketing expenses will continue to increase in
absolute dollars as the Company continues to expand its sales and marketing
efforts, establishes additional sales offices in the United States and
internationally and increases its promotional activities. These expenses are
expected to remain at a similar percentage of total revenues as the first three
months of 1999.

   General and Administrative.  General and administrative expenses consist
primarily of salaries and occupancy costs for administrative, executive and
finance personnel. General and administrative expenses increased to $8,210,000
for the three months ended March 31, 1999 from $4,567,000 for the three months
ended March 31, 1998 and as a percentage of total revenues was 6% for each of
the three months ended March 31, 1999 and 1998.  The increase in the absolute
dollar amount of general and administrative expenses was primarily due to
increased staffing and associated expenses necessary to manage and support the
Company's increased scale of operations.  The Company believes that its general
and administrative expenses will continue to increase in absolute dollars as a
result of the continued expansion of the Company's administrative staff and
facilities to support growing operations.  The Company anticipates that its
general and administrative expenses as a percentage of total revenues should
remain at a similar percentage as in the first three months of 1999.

Operating Income and Operating Margin

   Operating income increased to $31,477,000 for the three months ended March
31, 1999 from $13,676,000 for the three months ended March 31, 1998 and
operating margin increased to 23% in the first quarter 1999 from 18% in the
first quarter 1998. This increase in operating income and margin was due to
increases in license revenues without a proportional increase in cost,
particularly costs associated with the hiring of new personnel.

Other Income, Net

   Other income, net is primarily comprised of interest income earned on the
Company's cash and cash equivalents and short-term investments and reflects
earnings on increasing cash and cash equivalents and short-term investment
balances.

Provision for Income Taxes

   Income taxes are comprised primarily of federal and state taxes.  The
provision for income taxes was $12,532,000 and $5,520,000 for the three months
ended March 31, 1999 and 1998, respectively.  The provision for income taxes as
a percentage of pretax income was 37% and 36%, respectively.  The Company
expects its effective tax rate for the remainder of 1999 to be approximately
37%.

Net Income

   The Company had net income of $21,340,000 for the three months ended March
31, 1999 compared to net income of $9,748,000 for the three months ended March
31, 1998. Diluted net income per share increased to $0.20 per share in the first
quarter of 1999 from $0.10 per share in the comparable period in 1998. Net
income as a percentage of total revenues was 16% for the three months ended
March 31, 1999, compared to 13% for the three months ended March 31, 1998.

                                       14
<PAGE>
 
Liquidity and Capital Resources

   The Company's cash, cash equivalents and short-term investments decreased to
$230,464,000 as of March 31, 1999 from $231,849,000 as of December 31, 1998,
representing approximately 49% and 52% of total assets, respectively.  This
decrease was primarily attributable to an increase in accounts receivable, a
decrease in accrued expenses (attributable to payouts of final 1998 commissions
and bonuses and final income tax payments for 1998) and purchases of property
and equipment, partially offset by net income and increases in deferred revenue,
accounts payable and issuances of common stock under the Company's stock option
plans.  The Company's days sales outstanding (DSO) in accounts receivable was 99
as of March 31, 1999, compared with 90 as of December 31, 1998.  The Company
expects DSO to fluctuate significantly in future quarters.

   The Company has used fully serviced office suites on a month-to-month rental
basis to establish its presence in new locations.  As these locations expand,
the Company expects to transition more of the office suites to leased space.
This transition will involve build-out of tenant improvements, acquisition of
furniture and fixtures, and other capital costs, which were not incurred in
connection with the use of fully serviced office suites.  The Company has
already built-out leased facilities, both domestically and internationally, and
expects this trend to continue.

   Capital expenditures of the nature described above are expected to increase
during the remainder of 1999 and 2000.

   The Company believes that the anticipated cash flows from operations, cash,
cash equivalents and short-term investments will be adequate to meet its cash
needs for working capital and capital expenditures for at least the next twelve
months.

Year 2000 Preparedness

   Many existing computer programs and systems use only two-digit fields to
identify the year, e.g. 85=1985, and they are unable to process date and time
information between the twentieth and twenty-first centuries.  Accordingly,
computer programs and software may need to be modified prior to the year 2000 in
order to remain functional.  Failure to complete the necessary modifications
could cause a disruption or failure of such program and system.

   The Company's Y2K initiative is being managed by a team of internal staff and
third-party consultants specializing in Y2K issues.  The team's activities are
designed to identify potential Y2K problems and to ensure that there is no
adverse effect on our core business operations and that transactions with
clients, suppliers and financial institutions are fully supported.  The
Company's efforts have focused on three areas:  (i) the Company's products, (ii)
internal operating systems and (iii) interfaces with third-party systems.


 .    Products. The Company has put in place a certification program to verify
     the Y2K compliance of its products. Beginning with version 4.0 (Siebel 98),
     the Company's programs have been designed to be Y2K compliant. The Company
     has applied a number of test approaches and criteria to each of its
     products beginning with Siebel 98 and believes that all such products are
     Y2K compliant. While we believe that most of our currently developed and
     actively marketed products are Y2K compliant for significantly all
     functionality, our software products could contain errors or defects
     relating to Y2K. The Company has advised certain of its customers that
     internal testing of Y2K compliance should be conducted to ensure that the
     operations managed by Siebel products continue without disruption. If such
     modifications and conversions are not made, or are not completed in a
     timely manner, the Y2K issue could have a material adverse impact on our
     operations. The costs incurred to test the Company's products for Y2K
     compliance were incurred as normal product development expenses. Any
     additional expenses are expected to be minimal. 

 .    Internal Operating Systems.  The Company has implemented a plan to test all
     internal operating systems, such as computer hardware and software,
     telephone/PBX systems, fax machines, facilities systems such as building
     access and other miscellaneous systems on a worldwide basis.  The Company
     is approaching its Y2K internal readiness program in the following three
     phases:  (i) assessment, (ii) planning and (iii) implementation.  These  

                                       15
<PAGE>
 
     phases include such individual steps as taking an inventory of the
     Company's operating systems prioritized by risk, identifying failure dates,
     defining a solution strategy, estimating repair costs, identifying specific
     tasks necessary to ensure readiness, determining resource requirements and
     allocations, and finally, testing and fixing the operating systems as well
     as putting in place contingency plans for operating systems that have a
     high impact on the Company's business. The Company believes that, with
     modifications to existing software and conversions to new software, the Y2K
     issue will not pose significant operational problems to our internal
     operating systems. As of March 1999, the implementation phase is underway.
     However, if such modifications and conversions are not made, or are not
     completed in a timely manner, the Y2K issue could have a material adverse
     impact on our operations. Costs incurred to date and expected costs to
     complete this process are not expected to be material. 

 .    Third-Party Systems. The Company has developed a Y2K process for dealing
     with its key suppliers, distributors, vendors and system integrators and
     other partners. The Company has been in contact with its key third-party
     relationships regarding their Y2K compliance. The Company has received
     responses from its critical third-party relationships, most of whom have
     stated that they expect to address all of their significant Y2K issues in a
     timely manner. The Company is working to identify and analyze the most
     reasonably likely worst case scenarios for third party relationships
     affected by Y2K. These scenarios could include possible infrastructure
     collapse, the failure of water and power supplies, major transportation
     disruptions and failures of communications or financial systems any of
     which could have a material adverse effect on the Company's ability to
     deliver its products and services to its customers. While the Company has
     contingency plans in place to address most issues under its control, an
     infrastructure problem outside of its control could result in a delay in
     product shipments, depending on the nature and severity of the problems. As
     of February 1, 1999, the Company has initiated the process of analyzing its
     third-party systems and expects to complete the process by the fourth
     quarter. However, if such analyses and required modifications, if any, are
     not made, or are not completed in a timely manner, the Y2K issue could have
     a material adverse impact on our operations. Costs incurred to date and
     expected costs to complete this process are not expected to be material.

   Although the Company has spent a large amount of time and resource to address
potential Y2K problems, there is no assurance that the Company will be
successful in its efforts to identify and address all Y2K issues.  Even if the
Company acts in a timely manner to complete all of its assessments and planned
solutions, some problems may not be identified or corrected in time to prevent
material adverse consequences to the Company.  The discussion above regarding
estimated completion dates, costs, risks and other forward-looking statements
regarding Y2K is based on the Company's best estimates given information that is
currently available and is subject to change.  As the Company continues to
progress with its Y2K initiatives, it may discover that actual results will
differ materially from these estimates.  See "Factors Affecting Operating
Results -- Year 2000 Problems may cause an Interruption in our Business".


Factors Affecting Operating Results

   A Limited Operating History Upon Which to Evaluate our Business.  We began
operations in July 1993. We first shipped our Siebel Sales Enterprise product in
April 1995 and our Siebel Service Enterprise product in December 1996.
Subsequent versions of these products were first shipped in 1996 and 1997.
Accordingly, we have a limited operating history upon which you may evaluate our
business and prospects. You should evaluate our prospects in light of the risks,
expenses and uncertainties that companies in their early stage of development
frequently encounter.

   Net Revenue and Operating Results may Fluctuate.  Our net revenue and
operating results may fluctuate significantly because of a number of factors,
many of which are outside of our control. These factors include:


 .       Level of product and price competition;

 .       Length of our sales cycle and customer purchasing patterns;

 .       The size and timing of individual license transactions;

                                       16
<PAGE>
 
 .       Delay or deferral of customer implementations of our products;

 .       Success in expanding our customer support organization, direct sales
          force and indirect distribution channels;

 .       Timing of new product introductions and product enhancements;

 .       Appropriate mix of products and services sold;

 .       Levels of international sales;

 .       Activities of and acquisitions by competitors;

 .       Timing of new hires and the allocation of our resources;

 .       Changes in the economy and foreign currency exchange rates; and

 .       Our ability to develop and market new products and control costs.


   One or more of the foregoing factors may cause our operating expenses to be
disproportionately high during any given period or may cause our net revenue and
operating results to fluctuate significantly. Based on the preceding factors, we
may experience a shortfall in revenue or earnings or otherwise fail to meet
public market expectations, which could materially adversely affect our
business, financial condition and the market price of our common stock.

   Quarterly Operating Results may Fluctuate.  Our net revenue and operating
results may vary drastically from quarter to quarter. The main factors, which
may affect these fluctuations, are:

 .       The discretionary nature of our customer's purchase and budget cycles;

 .       The size and complexity of our license transactions;

 .       The potential delays in recognizing revenue from license transactions;

 .       The timing of new product releases;

 .       Seasonal variations in operating results; and

 .       Variations in the fiscal or quarterly cycles of our customers.


   Each customer's decision to implement our products and services is
discretionary, involves a significant commitment of resources and is subject to
their budget cycles. In addition, the timing of license revenue is difficult to
predict because of the length of our sales cycle, which has ranged to date from
two to eighteen months. We base our operating expenses on anticipated revenue
trends. Because a high percentage of these expenses are relatively fixed, a
delay in recognizing revenue from license transactions could cause significant
variations in operating results from quarter to quarter and could result in
operating losses. If these expenses precede, or are not subsequently followed
by, increased revenues, our operating results could be materially and adversely
affected. Although we have not experienced significant seasonal variations in
operating results, such variations could develop in the future.

   As a result of these and other factors, revenues for any quarter are subject
to significant variation, and we believe that period-to-period comparisons of
our results of operations are not necessarily useful. You should not rely on
these comparisons as indications of future performance. It is likely that our
future quarterly operating results from time to time will not meet the
expectations of market analysts or investors, which would likely have an adverse
effect on the price of our common stock.

                                       17
<PAGE>
 
   Reliance on Strategic Relationship with Systems Integrators.  We have
established strategic relationships with a number of organizations that we
believe are important to our sales, marketing and support activities and the
implementation of our products. We believe that our relationships with these
organizations provide marketing and sales opportunities for our direct sales
force and expand the distribution of our products. These relationships allow us
to keep pace with the technological and marketing developments of major software
vendors and provide us with technical assistance for our product development
efforts.

   In particular, we have established a non-exclusive strategic relationship
with Andersen Consulting, one of our principal stockholders. We have also
entered into significant relationships with other third-party systems
integrators such as PriceWaterhouseCoopers and Deloitte Consulting. A
significant portion of our revenues have historically been derived from
customers for whom Andersen Consulting, or another systems integrator with which
we have a significant relationship, have been engaged to provide system
integration services. Any deterioration of our relationship with these
significant third-party systems integrators could have a material adverse effect
on our business, financial condition and results of operations. We also have
relationships with Microsoft Corporation, Compaq Computer Corporation, Itochu
Corporation and Itochu Techno-Science Corporation, among others. Our failure to
maintain existing relationships, or to establish new relationships in the
future, could have a material adverse effect on our business, results of
operations and financial condition.

   Our current and potential customers may also rely on third-party system
integrators to develop, deploy and/or manage Siebel Enterprise Applications. If
we do not adequately train a sufficient number of system integrators, or if
these integrators do not have or devote the resources necessary to implement our
products, our business, operating results and financial condition could be
materially and adversely affected.

   The Internet Presents Unique Risks.  The Siebel Enterprise Applications
communicate through public and private networks over the Internet. The success
of our products may depend, in part, on our ability to continue developing
products which are compatible with the Internet. We cannot predict with any
assurance whether the Internet will be a viable commercial marketplace or
whether the demand for Internet-related products and services will increase or
decrease in the future.  The increased commercial use of the Internet could
require substantial modification and customization of our products and the
introduction of new products. We may not be able to effectively compete in the
Internet-related products and services market.

   Critical issues concerning the commercial use of the Internet, including
security, demand, reliability, cost, ease of use, accessibility, quality of
service and potential tax or other government regulation, remain unresolved and
may affect the use of the Internet as a medium to support the functionality of
our products and distribution of our software. If these critical issues are not
favorably resolved, our business, operating results and financial condition
could be materially and adversely affected.

   A Competitive and Rapidly Changing Market.  The market for client/server
application software is relatively new, highly competitive and rapidly changing.
We market our products only to customers who have migrated or are in the process
of migrating their enterprise computing systems to client/server computing
environments. Our future financial performance will partly depend on the
continued growth of organizations successfully adopting client/server-computing
environments. If the client/server market fails to grow or grows more slowly
than we currently anticipate, our business, operating results and financial
condition could be materially and adversely affected.

   The market for customer information software is also highly competitive and
rapidly changing. Our future financial performance will largely depend on growth
in the number of customer information applications developed for use in
client/server environments. If the customer information software market fails to
grow or grows more slowly than we currently anticipate, our business, operating
results and financial condition would be materially and adversely affected.

   Customers may not Successfully Implement our Products.  Many of our customers
purchase and implement our 

                                       18
<PAGE>
 
products in phases. Our customers frequently deploy our products to large
numbers of sales, marketing and customer service personnel. These end-users may
not accept our products. Our products are also being deployed on a variety of
computer hardware platforms and used with a number of third-party software
applications and programming tools. This use may present significant technical
challenges, particularly as large numbers of personnel attempt to use our
product concurrently. If existing customers have difficulty further deploying
Siebel Enterprise Applications or for any other reason are not satisfied with
Siebel Enterprise Applications, our business, operating results and financial
condition could be materially and adversely affected.

   A Limited Number of Products for our License Revenues.  In 1998 and the first
three months of 1999, a substantial majority of our license revenues were
attributable to sales of Siebel Sales Enterprise, Siebel Service Enterprise and
related products. We expect that such products and related consulting,
maintenance and training services will continue to account for a substantial
majority of our future revenues. As a result, factors adversely affecting the
pricing of or demand for such products, such as competition or technological
change, could have a material adverse effect on our business, operating results
and financial condition.

   The Length of Time Required to Engage a Client and to Implement Our Products
may be Lengthy and Unpredictable.  The timing of the sales and implementation of
our products and services is lengthy and not predictable with any degree of
accuracy. You should not rely on prior sales and implementation cycles as any
indication of future cycles.

   The license of our software products is often an enterprise-wide decision by
prospective customers and generally requires us to provide a significant level
of education to prospective customers regarding the use and benefits of our
products. In addition, the implementation of our products involves a significant
commitment of resources by prospective customers and is commonly associated with
substantial reengineering efforts that may be performed by the customer or
third-party system integrators. The cost to the customer of our product is
typically only a portion of the related hardware, software, development,
training and integration costs of implementing a large-scale sales and marketing
information system. For these and other reasons, the period between initial
contact and the implementation of our products is often lengthy and is subject
to a number of factors which may cause significant delays, many of which we have
little or no control over.  These factors include (i) the size and complexity of
our license transactions and (ii) delays in our customers' implementation of
client/server computing environments. A delay in the sale or implementation of
even a limited number of license transactions could have a material adverse
effect on our business and operations and cause our operating results to vary
significantly from quarter to quarter.

   Expanding Distribution May Create Additional Risks.  We have expanded the
distribution of our products in recent years. This expansion has placed new and
increased demands on our direct sales force and technical and sales support
staff. Our ability to achieve revenue growth in the future will depend, in part,
on our success in recruiting and training sufficient direct sales, technical and
customer support personnel. Although we invest significant resources to expand
our direct sales force and our technical and customer support staff, we have
experienced difficulty in recruiting qualified personnel. We also may not be
able to successfully expand our direct sales force or other distribution
channels. In addition, such expansion may not result in increased revenues. Any
failure to expand our direct sales force or technical and customer support staff
or to expand our distribution channels could materially and adversely affect our
business, operating results and financial condition.

   Revenue is Concentrated in a Relatively Small Number of Customers.  Our
success depends on maintaining relationships with our existing customers. A
relatively small number of customers have accounted for a significant percentage
of our revenues.  For 1998 and the three months ended March 31, 1999, sales to
our ten largest customers accounted for 22% and 34% of total revenues,
respectively.  We expect that sales of our products to a limited number of
customers will continue to account for a significant percentage of revenue for
the foreseeable future. The loss of a small number of customers or any reduction
or delay in orders by any such customer, or failure to successfully market our
products to new customers could have a material adverse effect on our business,
financial condition and results of operations.

  Success Requires us to keep Pace with Technological Developments, Evolving
Industry Standards and Changing 

                                       19
<PAGE>
 
Customer Needs. The software market in which we compete is characterized by (i)
rapid technological change, (ii) frequent introductions of new products, (iii)
changing customer needs, and (iv) evolving industry standards. To keep pace with
technological developments, evolving industry standards and changing customer
needs, we must support existing products and develop new products. We may not be
successful in developing, marketing and releasing new products or new versions
of the Siebel Enterprise Applications that respond to technological
developments, evolving industry standards or changing customer requirements. We
may also experience difficulties that could delay or prevent the successful
development, introduction and sale of these enhancements. In addition, these
enhancements may not adequately meet the requirements of the marketplace and may
not achieve any significant degree of market acceptance. If release dates of any
future products or enhancements to the Siebel Enterprise Applications are
delayed, or if these products or enhancements fail to achieve market acceptance
when released, our business, operating results and financial condition could be
materially and adversely affected. In addition, new products or enhancements by
our competitors may cause customers to defer or forgo purchases of our products,
which could have a material adverse effect on our business, financial condition
and results of operations.

   Success Requires us to Effectively Compete in the Customer Information
Systems Market. Our products target the customer information systems market.
This market is highly competitive, rapidly changing and significantly affected
by new product introductions. We face competition primarily from our customers'
internal information technology departments and systems integrators, as well as
from other application software providers that offer a variety of products and
services to address this market. Many of our customers and potential customers
have attempted to develop customer information systems, in-house either alone or
with the help of systems integrators. We may not be able to compete successfully
against such internal development efforts.

   We rely on a number of systems consulting and systems integration firms for
implementation and other customer support services, as well as for
recommendations of our products during the evaluation stage of the purchase
process. Although we seek to maintain close relationships with these service
providers, many of them have similar, and often more established, relationships
with our competitors. If we are unable to develop and retain effective, long-
term relationships with these third parties, our competitive position could be
materially and adversely affected. Further, many of these third parties have
significantly greater resources than we do and may market software products that
compete with us.


  The following table lists some of our current and potential competitors and
their products.


Company Name                                 Product
------------                                 -------
Acxiom.................................      DirectMedia
Baan N.V./Aurum Software, Inc..........      FrontOffice
Borealis Corporation...................      Arsenal
Clarify, Inc...........................      ClearSales, ClearSupport
Dendrite International, Inc............      Force One; Dendrite Series 6
Early Cloud & Co.......................      CallFlow
Exchange Applications..................      ValEX
IMA....................................      EDGE
Marketrieve Company....................      Marketrieve PLUS
Metrix, Inc............................      Field Service Dispatch
Onyx...................................      Customer Center
Oracle Corporation.....................      Oracle Sales and Marketing
Pegasystems, Inc.......................      PegaSURE; PegaWorks; PegaSales
Pivotal Software, Inc..................      Relationship
Prime Response.........................      Prime Vantage
Sales Vision...........................      Jsales
SAP A.G................................      Focus (not yet released)
Saratoga Systems.......................      Avenue
Symantec...............................      ACT!
The Vantive Corporation................      Vantive Enterprise

                                       20
<PAGE>
 
Trilogy Development Group, Inc.........      SC Config


   Some of these competitors have longer operating histories, significantly
greater financial, technical, marketing and other resources, significantly
greater name recognition and a larger installed base of customers than we do.
In addition, many competitors have well-established relationships with our
current and potential customers. As a result, these competitors may be able to
respond more quickly to new or emerging technologies and changes in customer
requirements, or to devote greater resources to the development, promotion and
sale of their products than we can.

   There are many factors that may increase competition in the customer
information systems market, including (i) entry of new competitors, (ii)
alliances among existing competitors and (iii) consolidation in the software
industry. Increased competition may result in price reductions, reduced gross
margins or loss of market share, any of which could materially adversely affect
our business, operating results and financial condition. If we cannot compete
successfully against current and future competitors or overcome competitive
pressures, our business, operating results and financial condition may be
adversely affected.

   If we do not Maintain our Relationship with Third-Party Vendors,
Interruptions in the Supply of Our Products may result. Portions of our products
incorporate software that was developed and is maintained by third-party
software developers. Although we believe there are other sources for these
products, any significant interruption in the supply of these products could
adversely impact our sales unless and until we can secure another source. We
depend in part on these third parties' abilities to enhance their current
products, to develop new products on a timely and cost-effective basis and to
respond to emerging industry standards and other technological changes. We may
not be able to replace the functionality provided by the third-party software
currently offered with our products if that software becomes obsolete or
incompatible with future versions of our products or is not adequately
maintained or updated. The absence of or any significant delay in the
replacement of that functionality could materially adversely affect our sales.

   Software Errors or Defects Could reduce Revenues.  Software products
frequently contain errors or failures, especially when first introduced or when
new versions are released.  Although we conduct extensive product testing during
product development, we have been forced to delay the commercial release of
products until the correction of software problems. We could lose revenues as a
result of software errors or defects. Our products are intended for use in sales
applications that may be critical to a customer's business. As a result, we
expect that our customers and potential customers will have a greater
sensitivity to product defects than the market for software products generally.
Testing errors may also be found in new products or releases after commencement
of commercial shipments, resulting in loss of revenue or delay in market
acceptance, damage to our reputation, or increased service and warranty costs,
any of which could have a material adverse effect upon our business, operating
results and financial condition.

   If we do not Successfully Manage Our Growth, our Business may be Negatively
Impacted.  Our business has grown rapidly in recent years. This growth has
placed a significant strain on our management systems and resources.  To manage
future growth we must continue to (i) improve our financial and management
controls, reporting systems and procedures on a timely basis and (ii) expand,
train and manage our employee work force. If we fail to manage our growth
effectively, our business, financial condition and results of operations could
be materially and adversely affected.

   The Loss of our Key Personnel Could Negatively Affect our Performance. Our
performance depends on the continued service of our key technical, sales and
senior management personnel, particularly Thomas M. Siebel, our Chairman and
Chief Executive Officer. None our key employees has entered into an employment
agreement with us. The loss of the services of one or more of our executive
officers could have a material adverse effect on our business, operating results
and financial condition.

   The Protection of Our Proprietary Information is Limited.  We rely primarily
on a combination of patent, copyright, trade secret and trademark laws,
confidentiality procedures and contractual provisions to protect our proprietary
rights. We also believe that the technological and creative skills of our
personnel, new product developments, frequent product enhancements, name
recognition and reliable product maintenance are essential to establishing and
maintaining a technology leadership position. We seek to protect our software,
documentation and 

                                       21
<PAGE>
 
other written materials under patent, trade secret and copyright laws, which
afford only limited protection. Any patents issued to us may be invalidated,
circumvented or challenged. Any of our pending or future patent applications,
whether or not being currently challenged, may not be issued with the scope of
the claims we seek, if at all. Furthermore, others may develop technologies that
are similar or superior to our technology or design around our patents. Despite
our efforts to protect our proprietary rights, unauthorized parties may attempt
to copy aspects of our products or to obtain and use information that we regard
as proprietary. Policing unauthorized use of our products is difficult. In
addition, the laws of some foreign countries do not protect our proprietary
rights as fully as do the laws of the United States. Our means of protecting our
proprietary rights in the United States or abroad may not be adequate. We have
entered into agreements with substantially all of our customers that require us
to place Siebel Enterprise Applications source code into escrow. Such agreements
generally provide that such parties will have a limited, non-exclusive right to
use such code if (i) there is a bankruptcy proceeding by or against us, (ii) we
cease to do business, or (iii) we fail to meet our support obligations.

   Although we do not believe that we are infringing any proprietary rights of
others, third parties may claim that we have infringed their intellectual
property rights. Furthermore, former employers of our former, current or future
employees may assert claims that such employees have improperly disclosed to us
the confidential or proprietary information of such former employers. Any such
claims, with or without merit, could (i) be time consuming to defend, (ii)
result in costly litigation, (iii) divert management's attention and resources,
(iv) cause product shipment delays, and (v) require us to pay money damages or
enter into royalty or licensing agreements. A successful claim of product
infringement against us and our failure or inability to license or create a
workaround for such infringed or similar technology may materially and adversely
affect our business, operating results and financial condition.

   We license certain software from third parties. These third-party software
licenses may not continue to be available to us on acceptable terms. The loss
of, or inability to maintain, any of these software licenses could result in
shipment delays or reductions. This could materially adversely affect our
business, operating results and financial condition.


   Year 2000 Problems may cause an Interruption in our Business.  Many existing
computer programs and systems use only two-digit fields to identify the year,
e.g. 85=1985, and they are unable to process date and time information between
the twentieth and twenty-first centuries.  Accordingly, computer programs and
software may need to be modified prior to the year 2000 in order to remain
functional. Although the Company has spent a large amount of time and resource
to address potential Y2K problems, there is no assurance that the Company will
be successful in its efforts to identify and address all Y2K issues.  Failure to
complete the necessary modifications could cause a disruption or failure of such
program and system. See "Management's Discussion and Analysis of Financial
Condition and Results of Operations--Year 2000 Preparedness".


   International Operations involve Unique Risks.  Our revenues are primarily
derived from large multi-national companies. To service the needs of these
companies, we must provide worldwide product support services. We have expanded,
and intend to continue expanding, our international operations and enter
additional international markets. This will require significant management
attention and financial resources that could adversely affect our operating
margins and earnings. We may not be able to maintain or increase international
market demand for Siebel Enterprise Applications. If we do not, our
international sales will be limited, and our business, operating results and
financial condition could be materially and adversely affected.

   Our international operations are subject to a variety of risks, including (i)
foreign currency fluctuations, (ii) economic or political instability, (iii)
shipping delays and (iv) various trade restrictions. Any of these risks could
have a significant impact on our ability to deliver products on a competitive
and timely basis. Significant increases in the level of customs duties, export
quotas or other trade restrictions could also have an adverse effect on our
business, financial condition and results of operations. In situations where
direct sales are denominated in foreign currency, any fluctuation in foreign
currency or the exchange rate may adversely affect our business, financial
condition and results of operations.


   Certain Stockholders may be able to Exercise Control over Matters Requiring
Stockholders Approval.   Our current officers, directors and entities affiliated
with us together beneficially owned a significant portion of the 

                                       22
<PAGE>
 
outstanding shares of common stock as of March 31, 1999. While these
stockholders do not hold a majority of the Company's outstanding common stock,
they will be able to exercise significant influence over matters requiring
stockholder approval, including the election of directors and the approval of
mergers, consolidations and sales of our assets. This may prevent or discourage
tender offers for our common stock.


   Stock Price may Continue to be Volatile. Our stock price has fluctuated
substantially since our initial public offering in June 1996. The trading price
of our common stock is subject to significant fluctuations in response to
variations in quarterly operating results, the gain or loss of significant
orders, changes in earning estimates by analysts, announcements of technological
innovations or new products by us or our competitors, general conditions in the
software and computer industries and other events or factors. In addition, the
stock market in general has experienced extreme price and volume fluctuations
which have affected the market price for many companies in industries similar or
related to ours and which have been unrelated to the operating performance of
these companies. These market fluctuations have adversely affected and may
continue to adversely affect the market price of our common stock.


   Certain Provisions in our Charter Documents may Prevent certain Corporate
Actions.   Our Board of Directors is authorized to issue up to 2,000,000 shares
of Preferred Stock and to determine the price, rights, preferences, privileges
and restrictions, including voting rights, of those shares without any further
approval by our stockholders. The Preferred Stock could be issued with voting,
liquidation, dividend and other rights superior to those of the common stock.
The rights of the holders of common stock will be subject to, and may be
adversely affected by, the rights of the holders of any Preferred Stock that may
be issued in the future. The issuance of Preferred Stock, while providing
desirable flexibility in connection with possible acquisitions and other
corporate purposes, could make it more difficult for a third party to acquire a
majority of our outstanding voting stock. We have instituted a classified Board
of Directors in our Certificate of Incorporation. This and certain other
provisions of our Certificate of Incorporation and certain provisions of our
Bylaws and of Delaware law, could delay or make more difficult a merger, tender
offer or proxy contest.

                                       23
<PAGE>
 
Item 3.  Quantitative and Qualitative Disclosures About Market Risk

   The tables below provide information about the Company's derivative financial
instruments and financial instruments that are subject to market risk.  These
include foreign currency forward contracts used to hedge foreign currency
receivables and intercompany balances, which are subject to exchange rate risk,
and available-for-sale short-term investments, which are subject to interest
rate risk.  The Company does not consider its cash equivalents to be subject to
interest rate risk due to their short maturities.


   The Company manages its foreign currency exchange rate risk by entering into
contracts to sell foreign currency at the time a foreign currency receivable is
generated.  When the foreign currency receivable is collected, the contract is
liquidated, thereby converting the foreign currency to US dollars and mitigating
the exchange rate risk.

   The Company manages its interest rate risk by maintaining an investment
portfolio with debt instruments of high credit quality and relatively short
average maturities.  The Company also manages interest rate risk by maintaining
sufficient cash and cash equivalent balances such that it is typically able to
hold its investments to maturity.

   The following summarizes the Company's foreign currency forward contracts,
all of which mature in 1999, by currency, as of March 31, 1999. Contract amounts
are representative of the expected payments to be made under these instruments
(unaudited, in thousands):



<TABLE>
<CAPTION>
                                             -------------------------------------------------
                                                 Contract         
                                                  Amount          Contract         Fair Value 
                                                  (Local           Amount         at March 31, 
                                                 Currency)           (US$)          1999 (US$)  
                                             --------------    -------------    ---------------
<S>                                          <C>                   <C>                  <C>
German marks (contracts to pay                                     
 DM/receive US$)..................              DM 1,200                 $668                $8 
British pounds (contracts to pay                                                                     
 (Pounds)/receive US$)............          (Pounds) 491                 $801                $11 
Japanese yen (contracts to pay                                                                       
 (Yen)/receive US$)...............       (Yen) 2,455,500              $20,557              $(100) 
</TABLE> 
 
 
    The following summarizes the Company's available-for-sale investments, as of
  March 31, 1999 (unaudited, in thousands):

<TABLE> 
<CAPTION> 
  

                                                                   Expected maturity date
                          -----------------------------------------------------------------------------------------
<S>                      <C>            <C>            <C>            <C>             <C>            <C>
                           1999             2000           2001            2002           2003        Thereafter
                          -----------    -----------    -----------    ------------    -----------    -------------

U S  treasury securities       --              --         $1,999           $3,054        $4,060           $2,954
                                                                                                  
 
Municipal securities       $35,478          $42,648      $30,707           $20,799        $1,990           $2,067
        

 
 
</TABLE>

                                       24
<PAGE>
 
                          Part II.  OTHER INFORMATION
                                        
ITEM 1.  LEGAL PROCEEDINGS

   In June 1996, Debra Christoffers, a former sales person of the Company, filed
a complaint for wrongful termination against the Company and Thomas Siebel, in
the Superior Court of California, County of San Mateo.  On May 15, 1998, a jury
returned verdicts in favor of Mr. Siebel and against the company for an
immaterial amount.  Both the plaintiff and the Company have filed notices of
appeal.  The Company intends to pursue the appeal vigorously and believes that
the ultimate outcome of the action will not have a material effect on the
Company's financial position or results of operations, although there can be no
assurance as to the outcome of such litigation.

   In March 1998, a purported class action complaint was filed against the
Company, Scopus Technology, Inc. ("Scopus") and the members of the Scopus board
of directors in the Superior Court of the State of California, County of Alameda
by a person claiming to be a Scopus stockholder.  Scopus became a wholly owned
subsidiary of the Company on May 18, 1998, upon the merger of a subsidiary of
the Company with and into Scopus (the "Merger").  The complaint alleges that the
Scopus board of directors breached its fiduciary duties to the shareholders of
Scopus in connection with its approval of the Merger.  The complaint further
alleges that the Company aided and abetted the alleged breach of fiduciary duty.
The complaint seeks monetary and other relief.  On October 26, 1998, the court
sustained defendants' demurrers to the complaint, with leave to amend.
Defendants' demurrers to the amended complaint are pending.  The Company
believes the suit is completely without merit and intends to continue to defend
itself vigorously, although there can be no assurance as to the outcome of such
litigation.


Item 2.  Changes in Securities and Use of Proceeds


   The effective date of the Company's first registration statement, filed on
Form S-1 under the Securities Act of 1933 (No. 333-12061) relating to the
Company's initial public offering of its Common Stock, was June 27, 1996. There
has been no change to the disclosure contained in the Company's report on Form
10-Q for the quarter ended March 31, 1998 regarding the use of proceeds
generated by the Company's initial public offering of its Common Stock.


Item 6.  Exhibits and Reports on Form 8-K


(a) Exhibits


Exhibit Number           Description of Document
--------------           -----------------------


2.1  Agreement and Plan of Merger and Reorganization, dated March 1,1998,
     among the Registrant, Syracuse Acquisition Sub, Inc. and Scopus Technology,
     Inc.(4)
3.1  Amended and Restated Certificate of Incorporation of the Registrant, as
     amended.(6)
3.2  Bylaws of the Registrant.(1)
4.1  Reference is made to Exhibits 3.1 and 3.2.
4.2  Specimen Stock Certificate.(1)
4.3  Restated Investor Rights Agreement, dated December 1, 1995, between the
     Registrant and certain investors, as amended April 30, 1996 and June 14,
     1996.(1)
10.1 Registrant's 1996 Equity Incentive Plan, as amended.(3)
10.2 Registrant's Employee Stock Purchase Plan, as amended.(3)
10.3 Form of Indemnity Agreement entered into between the Registrant and its
     officers and directors.(1)
10.4 Registrant's Deferred Compensation Plan, dated January 10,1997.(5)
10.5 Master Alliance Agreement, dated March 17, 1995, between the Registrant
     and Andersen Consulting  LLP.(1)(2)
10.6 Assignment Agreement, dated September 20, 1995, by and between the
     Registrant and Thomas M. Siebel.(1)
10.7 Lease Agreement, dated June 4, 1996, by and between the Registrant and
     Crossroad Associates and Clocktower Associates.(1)
27.1   Financial Data Schedule.(7)

_____________________

(1) Incorporated by reference to the Registrant's Registration Statement on Form
    S-1 (No. 333-03751), as amended.

                                       25
<PAGE>
 
(2) Confidential treatment has been granted with respect to portions of this
    exhibit.

(3) Incorporated by reference to the Registrant's Registration Statement on Form
    S-8 (No. 333-07983), as amended.


(4) Incorporated by reference to exhibit 99.1 of the Registrant's Current Report
    on Form 8-K filed by the Registrant on March 16, 1998.

(5) Incorporated by reference to the Registrant's Annual Report on Form 10-K for
    the year ended December 31, 1996.

(6) Incorporated by reference to the Registrant's Annual Report on Form 10-K for
    the year ended December 31, 1997.

(7) Filed herewith.



(b) Reports on Form 8-K

None

                                       26
<PAGE>
 
                                   SIGNATURES


Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                   SIEBEL SYSTEMS, INC.
        


Date:  May 14, 1999             By: /s/ Howard H. Graham
                                   ---------------------
                                    Howard H. Graham
                                    Senior Vice President Finance and
                                    Administration and
                                    Chief Financial Officer



                                By: /s/ Paul J. Gifford
                                   --------------------
                                    Paul J. Gifford
                                    Corporate Controller

                                       27