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                                                                   EXHIBIT 10.1

                    THIRD AMENDMENT TO THE AMENDED AND RESTATED 
                             COMMERCIAL LOAN AGREEMENT
                                          
This Third Amendment to the Amended and Restated Commercial Loan Agreement 
("Third Amendment") is entered into by and between The Titan Corporation, a 
Delaware corporation ("Borrower"), Sumitomo Bank of California, a California 
banking corporation ("Sumitomo"), and Imperial Bank, a California banking 
corporation ("Imperial") (Sumitomo and Imperial are collectively referred to 
herein as the "Banks"), and Sumitomo in its capacity as agent for Sumitomo 
and Imperial ("Agent"), and is dated as of March 27, 1998.  Reference is 
hereby made to (1) that certain Amendment to Agreement Re Release of Certain 
Titan Information Systems Corporation Collateral dated as of February 25, 
1998 ("Second Amendment"), (2) that certain Agreement Re Release of Certain 
Titan Information Systems Corporation Collateral dated as of December 8, 1997 
("First Amendment"), and (3) that certain Amended and Restated Commercial 
Loan Agreement dated as of May 15, 1997 by and between Borrower, the Banks, 
and Agent; collectively the "Loan Agreement".  Capitalized terms used but not 
otherwise defined herein shall have the meanings set forth in the Loan 
Agreement and Amendment to Existing Security Documents dated May 15, 1997.  
Any reference in the Amendment to Existing Security Documents to the Amended 
and Restated Commercial Loan Agreement, shall hereby be deemed to refer to 
the Loan Agreement.

                                     I. RECITALS

     A.        It is contemplated that Titan, or wholly-owned subsidiaries of
     Titan, will acquire one hundred percent (100%) of the common stock of
     Validity Corporation ("Validity"), and Horizons Technology, Inc.
     ("Horizons").  Banks have approved these acquisitions per the consent
     letter dated March 25, 1998.
     
     B.        In connection with these acquisitions, Borrower has requested
     that the Banks increase the Revolving Line of Credit to Thirty Million
     Dollars ($30,000,000).

     C.        The Banks are willing to grant this request on the terms and
     subject to the conditions set forth below.

                                   II. AMENDMENT
                                          
Now, therefore, it is hereby agreed by and between the parties hereto as
follows:

          1.   Paragraph 1.1(a) of the Loan Agreement is hereby restated in its
entirety as follows:

          1.1(a)    REVOLVING LINE OF CREDIT.  During the Availability Period,
Banks will provide a line of credit (the "Revolving Line of Credit") to
Borrower.  The maximum amount of the Revolving Line of Credit including the
subline facility for letters of credit (the "Total Commitment") is Thirty
Million Dollars ($30,000,000).  Of the Total Commitment, Sumitomo's Commitment
is Fifteen Million Dollars ($15,000,000) and Imperial's Commitment is Fifteen
Million Dollars ($15,000,000).  Upon execution of this Agreement, the respective
Commitments of the Banks shall be as set forth above.  Under no circumstances
shall any Bank be obligated to advance more than its particular Commitment.  The
respective Commitments of the Banks may be assigned pursuant to SECTION 9.1
hereof.  As used in this Agreement,


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"Pro Rata Share" means, as to any Bank at any time, the percentage equivalent 
(expressed as a decimal, rounded to the fifth decimal place) at such time of 
such Bank's Commitment DIVIDED BY the total Commitment of all Banks.  
Sumitomo's initial Pro Rata Share is 0.50 and Imperial's initial Pro Rata 
Share is 0.50.  Borrower's obligation to repay the Revolving Line of Credit 
is evidenced by two promissory notes (one in favor of Sumitomo and one in 
favor of Imperial) substantially in the forms of EXHIBITS A-1 AND A-2 
attached herewith (collectively, the "Revolving Line Notes").
          
          2.        Paragraph 1.2 is hereby restated in its entirety as follows:

          1.2       AVAILABILITY PERIOD.  The period under which Borrower may
draw on the Revolving line of Credit ("Availability Period") is between the date
of this Agreement and June 30, 1999 (the "Maturity Date"), unless Borrower is in
default, in which event Banks need not make any advances.

          3.        Paragraph 4.1(i) is hereby restated in its entirety as
                    follows:

     4.1(i)         RELEASE DOCUMENTS.  Within 5 business days of closing the
acquisitions of Validity Corporation and Horizons Technology, Inc., Agent shall
have received UCC-2 termination statements executed by the acquired companies'
secured parties, allowing for permitted liens under Paragraph 6.10, and such
other release documents as the Banks may require to release all liens in favor
of such parties with respect to all property covered by the Security Documents.

          4.        Paragraph 5.6 is amended only to the extent of replacing the
                    date "December 31, 1996" with "December 31, 1997".

          5.        Paragraph 6.2(e) is amended only to the extent of replacing
                    the number "30" in line two of that paragraph with "60".

          6.        Paragraph 6.3 is hereby restated in its entirety as follows:

          6.3       QUICK RATIO.  To maintain on a consolidated basis of the
                    last day of each quarter, a ratio of Quick Assets to current
                    liabilities of at least 1.05:1.00.  As used herein, "Quick
                    Assets" means cash, short-term cash investments, net trade
                    receivables and marketable securities not classified as
                    long-term investments.  For purposes of computing this
                    ratio, Current Liabilities shall include the outstanding
                    balance under the Revolving Line of Credit.

          7.        Paragraph 6.4 is hereby restated in its entirety as follows:

          6.4       NET WORTH.  To maintain on a consolidated basis as of the
                    last day of each calendar quarter, a Net Worth in an amount
                    at least equal to One Hundred and Three Million Dollars
                    ($103,000,000), PLUS an amount equal to seventy-five percent
                    (75%) of the cumulative sum of net income less cash
                    dividends for each calendar quarter beginning with the
                    calendar quarter ending June 30, 1998 and continuing on each
                    calendar quarter thereafter (with the quarterly step-ups in
                    the minimum Net Worth to be effective as of the last day of
                    each calendar quarter); and no reduction or deduction in the
                    permitted minimum Net Worth shall be made by reason of any
                    losses during any quarter.


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          8.        Paragraph 6.5 is hereby restated in its entirety as follows:

          6.5       TOTAL LIABILITIES TO TANGIBLE NET WORTH.  To maintain on a
                    consolidated basis of the last day of each quarter, a ratio
                    of Total Liabilities to Tangible Net Worth not exceeding
                    1.45:1.00 and, effective December 31, 1998 and thereafter, a
                    ratio not exceeding 1.25:1.00.  As used herein, (i) "Total
                    Liabilities" means the sum of current liabilities plus long
                    term liabilities, excluding the Subordinated Debt, and (ii)
                    "Tangible Net Worth" means book net worth minus intangible
                    assets (such as goodwill, patents, trademarks, trade names,
                    organization expense, treasury stock, unamortized debt
                    discount and expense, deferred research and development
                    costs, capitalized software costs, license fees, deferred
                    marketing expenses, and other like intangible, and monies
                    due from affiliates, officers, directors or shareholders of
                    Borrower) plus the Subordinated Debt.  Deferred income taxes
                    shall not be deemed intangible assets.

          9.        Paragraph 6.6 is hereby restated in its entirety as follows:

          6.6       PROFITABILITY.  To maintain on a consolidated basis a
                    positive net income before taxes and extraordinary items and
                    a positive net income after taxes and extraordinary items on
                    an annual basis and not to experience two consecutive
                    quarters of losses.

          10.       Paragraph 6.7 is hereby deleted in its entirety.

          11.       Paragraph 6.8 is hereby restated in its entirety as follows:

          6.8       FIXED CHARGE COVERAGE RATIO.  To maintain on a consolidated
                    basis a Fixed Charge Coverage Ratio of at least 1.15:1.00. 
                    "Fixed Charge Coverage Ratio" means the sum of net income
                    (or net loss), plus gross interest expense, plus
                    depreciation, plus non-cash amortization, minus
                    extraordinary income/gains, plus extraordinary non-cash
                    expenses/losses, minus gains (or plus losses) on
                    sales/dispositions of fixed assets, less capital
                    expenditures (net purchase money financing), less any cash
                    payments made under the terms of any acquisition agreements
                    with regards to seller financing and covenants not to
                    compete, less cash dividends, less cash stock purchases
                    DIVIDED BY the sum of gross interest expense plus current
                    portion of all indebtedness including capital leases.  This
                    covenant shall be measured beginning June 30, 1998. 
                    Calculation of this ratio (a) through December 31, 1998
                    shall be on the basis of year-to-date income statement
                    results annualized, and (b) on a rolling four quarter basis
                    thereafter; in either case, the balance sheet items shall
                    not be annualized.

          12.       Paragraph 6.9(d) is hereby restated in its entirety as
                    follows:

          6.9(d)    Debt and lease obligations reflected in the December 31,
                    1997 fiscal year end financial statement of Borrower
                    submitted to Agent and Banks.


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          13.       Paragraph 6.10(c) is hereby restated in its entirety as
                    follows:
     
          6.10(c)   Liens disclosed in the December 31, 1997 fiscal year end
                    financial statement of Borrower submitted to Agent and
                    Banks.
     
          14.       Paragraph 6.13 is hereby restated in its entirety as
                    follows:
          
          6.13      LOANS TO OFFICERS.  Not to make any loans, advances, stock
                    purchases, capital contributions or other extensions of
                    credit to any of Borrower's executives, officers, directors,
                    shareholders, employees (or any relative of any of the
                    foregoing) or affiliates (i.e. companies which are minority
                    owned or whose results are not consolidated in Borrower's
                    financial statements) in excess of $75,000 to one individual
                    or $400,000 in total in any fiscal year (other than those
                    reflected in Borrower's December 31, 1997 fiscal year end
                    financial statements).
     
          15.       Paragraph 6.14 is hereby restated in its entirety as
                    follows:

          6.14      Not to, without the prior written consent of all Banks
                    (which consent will not be unreasonably withheld), acquire
                    or purchase a business or its assets for a consideration
                    (including assumption of debt, seller financing and net
                    present value of covenants not to compete) in excess of One
                    Million Dollars ($1,000,000).
     
          16.       Paragraph 6.26 is restated in its entirety as follows:
     
          6.26      Borrower will not transfer any of Borrower's assets to 
                    any subsidiary, affiliate or related entity without first 
                    obtaining the written consent of Banks, which consent 
                    shall not be unreasonably withheld in the case of a 
                    transfer of assets to a wholly owned subsidiary.  At any 
                    time that Borrower forms a new subsidiary, affiliate, or 
                    other related entity, it will immediately notify the 
                    Banks of such formation and will, upon request of Agent 
                    or either of the Banks, execute and deliver a continuing 
                    guaranty, security agreement, and financing statement 
                    (UCC-1), together with such other documents required by 
                    Agent or either of the Banks, executed by such entity, 
                    providing assurance to Banks that Banks' lien on all of 
                    Borrower's assets and the assets of Borrower's 
                    subsidiaries, affiliates and related entities is a first 
                    lien on all such assets (and, without limiting the 
                    foregoing, Agent and Banks may condition the transfer of 
                    any such assets on the execution and delivery of such 
                    guaranties, security agreements, financing statements and 
                    other such documents).  Borrower represents and agrees 
                    that at all times the security interest and lien of the 
                    Agent and the Banks in all assets of the Borrower and 
                    each of Borrower's subsidiaries, affiliates or related 
                    entities as to which security agreements, financing 
                    statements or other security documents have been 
                    provided, shall at all times remain a first position 
                    security interest and lien against such assets, subject 
                    to no other financing statements, liens or other prior 
                    encumbrances of any nature whatsoever; and Borrower shall 
                    at all times take all such actions as are

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                    necessary to maintain the first position priority of the
                    security interests and liens of Agent and Banks with respect
                    to the assets of Borrower and all such subsidiaries,
                    affiliates and other related entities.
          
          17.       As additional consideration for entering into this
                    Agreement, Borrower shall pay to Agent (a) for the sole
                    benefit of Agent, a fee of Seven Thousand and Five Hundred
                    Dollars ($7,500.00) which shall be payable substantially
                    concurrently with the execution of this Agreement and on
                    each anniversary thereafter, and (b) for the ratable benefit
                    of Banks a commitment fee in the amount of Seventy Five
                    Thousand Dollars ($75,000.00), which shall be payable
                    substantially concurrently with the execution of this
                    Agreement.

          18.       The Loan Agreement and the existing security documents
                    remain unmodified and in full force and effect, except as
                    otherwise amended hereby and the occurrence of any default
                    under this Amendment or the failure by Borrower to observe
                    or perform any term, covenant or agreement contained in this
                    Amendment, shall be deemed to be a default under the Loan
                    Agreement and other Loan Documents.

          19.       The Revolving Line Note in favor of Sumitomo is hereby
                    amended and restated in its entirety as set forth on Exhibit
                    A-1 hereto, and the Revolving Line Note in favor of Imperial
                    is hereby amended and restated in its entirety as forth on
                    Exhibit A-2 hereto.  In connection herewith, Borrower shall
                    execute each of the Amended Revolving Line Notes in favor of
                    Sumitomo and Imperial.

          20.       Agent may condition the effectiveness of this Third
                    Amendment on all of the following conditions being satisfied
                    (any of which Agent may, in its sole and absolute
                    discretion, waive):

               a.        Agent shall have received fully executed originals of
               this Third Amendment;
          
               b.        The Consent of Guarantors, Grantors and Pledgors
               attached hereto shall be fully executed by each of the parties
               indicated therein;

               c.        Borrower shall have paid all of the fees required in
               this Third Amendment, and any and all costs and expenses incurred
               by Agent, including without limitation reasonable attorneys'
               fees, in connection with this Third Amendment and the matters
               described herein; and

               d.        Borrower shall deliver such additional documentation
               and information to Agent as Agent reasonably requests.

               This Amendment is executed as of the date first written above.

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                              "Borrower"

                              THE TITAN CORPORATION, A Delaware
                              corporation

                              By:/S/ ERIC M. DEMARCO
                                 --------------------
                                 Eric M. DeMarco
                                 Senior Vice President
                                 Chief Financial Officer
                                          
                                          
                                          
                              "Banks"
                                          
                              THE SUMITOMO BANK OF CALIFORNIA,
                              a California banking corporation,
                              in its individual capacity

                              By:/S/ SAJEDA SIMJEE
                                 -----------------------------
                                 Sajeda Simjee, Vice President
                                          
                                          
                              IMPERIAL BANK, a California banking
                              corporation
 
                               By:/S/ MICHAEL A. BERRIER
                                  -----------------------
                                  Michael A. Berrier, Vice
                                     President
                                          
                                          
                              "Agent"
                              THE SUMITOMO BANK OF CALIFRONIA, a
                              California banking corporation, as
                              Agent for itself and Imperial Bank
            
            
                              By:/S/ SAJEDA SIMJEE
                                 -----------------------------
                                 Sajeda Simjee, Vice President