<PAGE>

                     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, 1998

     
                                      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 0-27146

                              AMERIN CORPORATION
               (Exact name of registrant as specified in its charter)

          Delaware                                            11-3085148
     (State or other jurisdiction of                       (I.R.S. Employer
     incorporation or organization)                        Identification No.)

     200 E. Randolph Drive, 49th Floor, Chicago, IL          60601-7125 
        (Address of principal executive offices)              (Zip Code)

     Registrant's telephone number, including area code:  (312) 540-0078  

     Indicate by check mark whether the registrant: (1) has filed all reports
required to be filed by Section 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
                                      --------       -------

                 APPLICABLE ONLY TO ISSUER'S INVOLVED IN BANKRUPTCY
                    PROCEEDINGS DURING THE PRECEDING FIVE YEARS

     Indicate by check mark whether the registrant has filed all documents and
reports required to be filed by Section 12, 13 or 15(d) of the Securities
Exchange Act of 1934 subsequent to the distribution of securities under a plan
confirmed by a court.
                                   Yes          No
                                        -----       ------

                        APPLICABLE ONLY TO CORPORATE ISSUERS

     Indicate the number of shares outstanding of each of the issuer's 
classes of common stock, as of the latest practicable date.

          
                      Class                       Outstanding at May 1, 1998
                -------------------               --------------------------
     Voting Common Stock, $.01 per value                    24,704,813
     Nonvoting Common Stock, $.01 per value                  1,656,909


<PAGE>

                                          
                                 AMERIN CORPORATION
                                 TABLE OF CONTENTS

                                                                          PAGE

PART I.  FINANCIAL INFORMATION

   ITEM 1. Financial Statements:

      Condensed Consolidated Balance Sheets at
         March 31, 1998 (unaudited) and December 31, 1997. . . . . . . . .  1

      Condensed Consolidated Statements of Operations for the
         Three Month Periods Ended March 31, 1998 and 1997 (unaudited) . .  2

      Condensed Consolidated Statements of Cash Flows for the
         Three Month Periods Ended March 31, 1998 and 1997 (unaudited) . .  3

      Notes to Condensed Consolidated Financial Statements (unaudited) . .  4

   ITEM 2. Management's Discussion and Analysis of Financial
           Condition and Results of Operations . . . . . . . . . . . . . .  5
 
PART II.  OTHER INFORMATION

   ITEM 6. Exhibits and Reports on Form 8-K. . . . . . . . . . . . . . . .  8





                                       i

<PAGE>


                           PART I. FINANCIAL INFORMATION

ITEM 1.  FINANCIAL STATEMENTS
                                          
                       AMERIN CORPORATION AND SUBSIDIARIES
                                          
                      CONDENSED CONSOLIDATED BALANCE SHEETS

<TABLE>
<CAPTION>

                                                          MARCH 31,                DECEMBER 31,
                                                             1998                     1997
                                                         -----------               ------------
                                                         (UNAUDITED)
                                                               (IN THOUSANDS OF DOLLARS)
<S>                                                       <C>                      <C>
ASSETS
Investments:
   Fixed maturities available-for-sale, at fair value. . .  $  388,697              $  374,320
   Short-term investments. . . . . . . . . . . . . . . . .       6,026                   3,400
                                                            ----------              ----------
Total investments. . . . . . . . . . . . . . . . . . . . .     394,723                 377,720
Cash and cash equivalents. . . . . . . . . . . . . . . . .       7,467                   4,456
Accrued investment income. . . . . . . . . . . . . . . . .       5,380                   5,872
Premiums receivable. . . . . . . . . . . . . . . . . . . .       6,596                   5,020
Deferred policy acquisition costs. . . . . . . . . . . . .       8,998                   7,776
Leasehold improvements, furniture and equipment, at cost,
   net of accumulated depreciation . . . . . . . . . . . .       9,779                   9,315
Goodwill, net of accumulated amortization. . . . . . . . .       2,096                   2,133
Other assets . . . . . . . . . . . . . . . . . . . . . . .       4,535                   3,009
                                                            ----------              ----------
Total assets . . . . . . . . . . . . . . . . . . . . . . .  $  439,574              $  415,301
                                                            ----------              ----------
                                                            ----------              ----------

LIABILITIES AND COMMON STOCKHOLDERS' EQUITY
Liabilities:
   Loss reserves . . . . . . . . . . . . . . . . . . . . .  $   35,407              $   31,280
   Unearned premiums . . . . . . . . . . . . . . . . . . .      22,999                  23,352
   Current income taxes. . . . . . . . . . . . . . . . . .       2,883                     790
   Deferred income taxes . . . . . . . . . . . . . . . . .       5,066                   5,015
   Payable for securities. . . . . . . . . . . . . . . . .       7,034                     ---
   Accrued expenses and other liabilities. . . . . . . . .       3,689                   4,709
                                                            ----------              ----------
   Total liabilities . . . . . . . . . . . . . . . . . . .      77,078                  65,146

Common Stockholders' Equity:
   Voting Common Stock, $.01 par, 50,000,000 shares authorized, 
      24,584,851 shares and 24,488,725 shares issued and 
      outstanding in 1998 and 1997, respectively . . . . .         245                     245
   Nonvoting Common Stock, $.01 par, 50,000,000 shares 
      authorized, 1,656,909 shares issued and outstanding
      in 1998 and 1997 . . . . . . . . . . . . . . . . . .          17                      17
   Additional paid-in capital. . . . . . . . . . . . . . .     317,949                 316,642
   Accumulated other comprehensive income. . . . . . . . .       7,312                   8,229
   Retained earnings . . . . . . . . . . . . . . . . . . .      36,973                  25,022
                                                            ----------              ----------
Total common stockholders' equity. . . . . . . . . . . . .     362,496                 350,155
                                                            ----------              ----------
   Total liabilities and common stockholders' equity . . .  $  439,574            $    415,301
                                                            ----------              ----------
                                                            ----------              ----------
</TABLE>

                                  See accompanying notes.

                                       1

<PAGE>

   
                             AMERIN CORPORATION AND SUBSIDIARIES

                      CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS


<TABLE>
<CAPTION>

                                                        THREE MONTHS ENDED
                                                              MARCH 31,
                                                      1998                 1997
                                                      ----                 ----
                                                            (UNAUDITED)
                                          (IN THOUSANDS OF DOLLARS, EXCEPT PER SHARE DATA)
<S>                                                   <C>                   <C>

Revenues:
   Net premiums written .............................. $ 27,162              $  20,424
   Decrease in unearned premiums......................      447                     67
                                                       --------              ---------
   Net premiums earned ...............................   27,609                 20,491
   Net investment income .............................    5,088                  4,483
   Realized investment gains (losses) ................      430                    (22)
                                                       --------              ---------
Total revenues........................................   33,127                 24,952

Expenses:
     Losses incurred..................................    9,334                  6,630
     Policy acquisition costs ........................    3,939                  2,539
     Underwriting and other expenses .................    3,175                  3,616
                                                       --------              ---------
Total expenses .......................................   16,448                 12,785
                                                       --------              ---------
Income before income taxes ...........................   16,679                 12,167
Income taxes .........................................    4,729                  3,498
                                                       --------              ---------
Net income ........................................... $ 11,950              $   8,669
                                                       --------              ---------
                                                       --------              ---------
Net income per common share:
     Basic ..........................................  $    .46              $     .33
     Diluted ........................................  $    .45              $     .33
Average common and common equivalent shares 
  outstanding........................................  26,666.0               26,357.9
</TABLE>

                                      See accompanying notes.


                                       2

<PAGE>

                        AMERIN CORPORATION AND SUBSIDIARIES
                   CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

<TABLE>
<CAPTION>

                                                                  THREE MONTHS ENDED MARCH 31
                                                                  ---------------------------
                                                                  1998                   1997
                                                                  ----                   ----
                                                                          (UNAUDITED)
                                                                  (IN THOUSANDS OF DOLLARS)
<S>                                                             <C>                    <C>
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income ...................................................  $ 11,950               $ 8,669
Adjustments to reconcile net income to net cash
        provided by operating activities:
    Change in:
          Accrued  investment income and premiums receivable .    (1,084)                  731
          Loss reserves.......................................     4,127                 3,758
          Unearned premiums ..................................      (353)                  (57)
          Accounts payable and accrued expenses ..............      (978)               (1,529)
          Federal income taxes ...............................     2,638                 2,791
Policy acquisition costs deferred ............................    (2,558)               (2,360)
Policy acquisition costs amortized ...........................     1,336                 2,395
Depreciation and other amortization ..........................       543                   334
Realized investment (gains) losses ...........................      (430)                   22
Other items, net .............................................    (1,352)               (1,016)
                                                                 --------              --------
Net cash provided by operating activities ....................    13,839                13,738                 
                                                                 --------              --------
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of:             
     Fixed maturity securities ...............................   (33,281)              (31,768)
     Property and equipment ..................................      (969)                 (300)
     Short-term investments, net .............................    (2,626)               11,189
Sale or maturity of:
     Fixed maturity securities ...............................    24,740                 7,453
     Property and equipment ..................................       ---                     1
                                                                 --------              --------
Net cash used by investing activities ........................   (12,136)              (13,425)
                                                                 --------              --------

CASH FLOWS FROM FINANCING ACTIVITIES
Issuance of common stock .....................................     1,308                   342
                                                                 --------              --------
Net cash provided by financing activities ....................     1,308                   342
                                                                 --------              --------
Net increase in cash and cash equivalents.....................     3,011                   655
Cash and cash equivalents at beginning of period .............     4,456                 1,176
                                                                 --------              --------
Cash and cash equivalents at end of period ...................  $  7,467               $ 1,831
                                                                 --------              --------
                                                                 --------              --------
</TABLE>

                        See accompanying notes.

                                       3

<PAGE>

                        AMERIN CORPORATION AND SUBSIDIARIES
                NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS
                                 MARCH 31, 1998
                                   (UNAUDITED)

1.   ACCOUNTING POLICIES

BASIS OF PRESENTATION

The accompanying unaudited condensed consolidated financial statements have 
been prepared in accordance with generally accepted accounting principles for 
interim financial information and with the requirements of Form 10-Q.  
Accordingly, they do not include all of the information and footnotes 
required by generally accepted accounting principles for complete financial 
statements.  In the opinion of management, all adjustments (consisting only 
of normal recurring accruals) considered necessary for a fair presentation 
have been included. Operating results for the three month period ended March 
31, 1998, are not necessarily indicative of the results that may be expected 
for the year ending December 31, 1998.  For further information, refer to the 
consolidated financial statements and footnotes thereto included in the 
Company's Annual Report on Form 10-K for the year ended December 31, 1997.

NEW AUTHORITATIVE PRONOUNCEMENT

In June 1997, the Financial Accounting Standards Board issued Statement of 
Financial Accounting Standards No. 131 (SFAS 131) "Disclosure about Segments 
of an Enterprise and Related Information," which is effective for years 
beginning after December 15, 1997.  SFAS 131 established standards for the 
way that public business enterprises report information about operating 
segments in annual financial statements and requires that those enterprises 
report selected information about operating segments in interim financial 
reports.  However, segment information is not required to be reported in 
interim financial statements in the initial year of adoption.  SFAS 131 also 
establishes standards for related disclosures about products and services, 
geographic areas and major customers.  Implementation of this standard is not 
expected to have a material effect on the Company's Financial statements.

2.   INCOME TAXES

The provision for income taxes varies from the statutory federal income tax 
rate applied to income before income taxes principally due to tax exempt 
interest.

                                       4

<PAGE>


3.   NET INCOME PER COMMON SHARE

The following table sets forth the computation of net income per common share
(in thousands, except per share data):

<TABLE>
<CAPTION>

                                                        Three months ended March 31
                                                        ---------------------------
                                                         1998                  1997
                                                         ----                  ----
<S>                                                     <C>                    <C>
 Net income                                             $  11,950              $ 8,669
                                                        ---------              -------
 Weighted average number of common shares outstanding      26,193               26,086
 Dilutive effect of stock options using the
    treasury stock method                                     473                  272
                                                        ---------              -------
 Weighted average number of common and common
    equivalent shares outstanding                          26,666               26,358
                                                        ---------              -------
 Net income per common share:
      Basic                                             $     .46              $   .33
      Diluted                                           $     .45              $   .33
</TABLE>


Where the effect of common stock equivalents on net income or loss per share 
would be antidilutive, they are excluded from the average common and common 
equivalent shares outstanding.

4.   COMPREHENSIVE INCOME

As of January 1, 1998, the Company adopted the interim reporting requirements 
of Statement of Financial Accounting Standards No. 130 (SFAS 130), "Reporting 
Comprehensive Income."  SFAS 130 establishes new rules for the reporting and 
display of comprehensive income and its components; however, the adoption of 
SFAS 130 had no impact on the Company's net income or stockholders' equity. 
SFAS 130 requires unrealized gains or losses on the Company's available for 
sale securities, which prior to adoption were reported separately in 
stockholders' equity, to be included in other comprehensive income.  Prior 
year consolidated financial statements have been reclassified to conform to 
the requirements of SFAS 130.

The components of comprehensive income and accumulated other comprehensive 
income are as follows (in thousands):


<TABLE>
<CAPTION>
                                                     Three months ended March 31
                                                     ---------------------------
                                                      1998                  1997
                                                      ----                  ----

<S>                                                  <C>                  <C>
 Net income.......................................   $  11,950            $  8,669
 Net change in unrealized gain on available for
   sale securities, net of income taxes of
   $(494) and $(1,909), respectively .............        (917)              (3546)
                                                     ---------            --------
 Comprehensive income ............................   $  11,033            $  5,123
                                                     ---------            --------
                                                     ---------            --------

 Accumulated other comprehensive income at
   beginning of period ...........................   $   8,229            $    222
 Net change in unrealized gain on available
   for sale securities, net of income taxes ......        (917)             (3,546)
                                                     ---------            --------
 Accumulated other comprehensive income at
   end of period..................................   $   7,312            $ (3,324)
                                                     ---------            --------
                                                     ---------            --------
</TABLE>

                                       5


<PAGE>

ITEM 2.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
         CONDITION AND RESULTS OF OPERATIONS

RESULTS OF OPERATIONS

     THREE MONTHS ENDED MARCH 31, 1998 COMPARED TO THREE MONTHS ENDED MARCH 
31, 1997.  Net premiums written for the three months ended March 31, 1998 
were $27.2 million compared to $20.4 million for the three months ended March 
31, 1997, which represents a 33% increase.  The increase was primarily 
attributable to growth in insurance in force and related renewal premiums of 
the Company's primary insurance subsidiary, Amerin Guaranty Corporation 
("Amerin Guaranty"). Management believes that Amerin Guaranty was able to 
increase revenues due primarily to increased use by existing lenders of the 
Company's borrower-paid mortgage insurance and the addition of new lenders 
which began doing business with the Company during the last year.  Amerin 
Guaranty's monthly premium plan represented 89.2% of new insurance written 
for the three months ended March 31, 1998 compared to 91.2% for the same 
period in 1997.

     Net premiums earned increased by $7.1 million to $27.6 million for the 
three months ended March 31, 1998 from $20.5 million for the three months 
ended March 31, 1997.  This increase was primarily due to the increase in 
insurance written and in force in the 1998 period over the corresponding 
portion of the 1997 period.

     Net investment income of $5.1 million for the three months ended March 
31, 1998 increased by $.6 (or 13%) over the same period in 1997 primarily due 
to investment of the proceeds of Amerin Guaranty's net operating cash flows 
over the course of 1997 and the first three months of 1998.  Realized 
investment gains for the three months ended March 31, 1998 were $430,000 
compared to realized investment losses of $22,000 for the same period in 1997.

     Losses incurred in the three months ended March 31, 1998 were $9.3 
million, compared to $6.6 million of losses incurred in the three months 
ended March 31, 1997, as a result of the aging of the Company's policies and 
growth in insurance in force.  Because of the Company's limited operating 
history, its loss experience is expected to significantly increase as its 
policies age further. Policy acquisition costs during the three months ended 
March 31, 1998 of $3.9 million increased by $1.4 million (or 55%) compared to 
the same period in 1997 principally due to the growth in the level of 
marketing and underwriting activity in connection with the increased 
production of new insurance written in the 1997 period compared to the prior 
year period.  Underwriting and other expenses decreased by $.4 million (or 
12%) for the three months ended March 31, 1998 over the same period in 1997 
due to expenses incurred in connection with the Company's secondary offering 
completed in February, 1997.

     The Company's effective tax rate was 28% in the three months ended March 
31, 1998 compared to 29% for the same period in 1997.  The effective tax rate 
for the first quarter of 1998 and 1997 was below the statutory rate of 35%, 
reflecting the benefits of tax-preferenced investment income.

     As a result of the foregoing factors, the Company had net income of 
$12.0 million for the three months ended March 31, 1998, compared to net 
income of $8.7 million for the same period in 1997.

LIQUIDITY AND CAPITAL RESOURCES

     The liquidity and capital resource considerations are different for 
Amerin Corporation and its principal insurance operating subsidiary, Amerin 
Guaranty, as discussed below.

                                       6

<PAGE>

     Amerin Corporation is a holding company whose principal assets are its 
investments in Amerin Guaranty and Amerin Re. Amerin Corporation has no 
operations of its own and no employees and has only limited needs for 
liquidity to meet certain legal, accounting, tax and administrative expenses. 
 Amerin Corporation relies primarily on dividends and other permitted 
distributions from Amerin Guaranty and Amerin Re as sources of funds.  Amerin 
Corporation does not currently have any committed lines of credit.

     The principal sources of funds for Amerin Guaranty are premiums received 
on new and renewal business, amounts earned from the investment of its 
contributed capital as well as the investment of its cash flow and 
commissions on ceded business and reimbursement of losses from reinsurers.  
The principal uses of funds by Amerin Guaranty are the payment of claims and 
related expenses, reinsurance premiums, other operating expenses and 
dividends to Amerin Corporation.  Liquidity requirements are influenced 
significantly by the level of claims incidence.  Amerin Guaranty does not 
currently have any committed lines of credit.

     Amerin Guaranty generates substantial cash flows from operations as a 
result of premiums being received in advance of the time when claim payments 
are required.  Cash flows generated from Amerin Guaranty's mortgage insurance 
operations totaled $16.6 million and $14.1 million for the first three months 
of 1998 and 1997, respectively.  These operating cash flows, along with that 
portion of the investment portfolio that is held in cash and highly liquid 
securities, are available towards the liquidity requirements of Amerin 
Guaranty. Amerin Guaranty's investment portfolio was $352.8  million at March 
31, 1998 and $333.3 million at December 31, 1997.

     All of the Company's $388.7 million of fixed income securities at March 
31, 1998 are rated "investment grade," which is defined by the Company as a 
security having a National Association of Insurance Commissioners ("NAIC") 
rating of 1 or 2 or an S&P rating ranging from "AAA" to "BBB-."

     RISK TO CAPITAL RATIO.  As a condition to maintenance of its 
claims-paying ratings, the total amount of insurance risk that may be written 
by Amerin Guaranty is limited to a multiple of 20 times its statutory capital 
(which includes the contingency reserve) less the carrying value of 
non-investment grade debt and tax and loss bonds and investments in 
affiliates, or such higher or lower multiple as is reasonably determined by 
the rating agency in its sole discretion.  Amerin Guaranty has several 
alternatives available to control its risk to capital ratio, including 
obtaining capital contributions from the Company, purchasing  reinsurance and 
reducing the amount of new business written.  A material reduction in 
statutory capital, whether resulting from underwriting or investment losses 
or otherwise, or a disproportionate increase in risk in force, could increase 
the risk to capital ratio.  An increase in the risk to capital ratio could 
limit Amerin Guaranty's ability to write new business (which in turn could 
materially adversely affect the Company's results of operations and 
prospects).  At March 31, 1998 and December 31, 1997, Amerin Guaranty's risk 
to capital ratio was 16.4 to 1 and 16.1 to 1, respectively.

                                       7


<PAGE>

                            PART II.  OTHER INFORMATION


ITEM 4.   SUBMISSION OF MATTERS TO A VOTE OF SECURITY-HOLDERS


     No matters were submitted to a vote of holders of the Company's securities
in the first quarter.


ITEM 6.   EXHIBITS AND REPORTS ON FORM 8-K

a)   Exhibits

     See Exhibit Index on Page E-1 for exhibits filed with this report on
Form 10-Q.

b)   Reports on Form 8-K

     The Registrant did not file any reports on Form 8-K during the quarter
for which this report on Form 10-Q is filed.



                                       8

<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.


                                         AMERIN CORPORATION


Date:  May 13, 1998                      By: /s/ Gerald L. Friedman
                                             ----------------------
                                             Gerald L. Friedman
                                             Chairman of the Board and
                                             Chief Executive Officer


Date:  May 13, 1998                      By: /s/ David I. Vickers
                                             --------------------
                                             David I. Vickers
                                             Senior Vice President
                                             Chief Financial Officer





                                       9


<PAGE>

                                 INDEX TO EXHIBITS




     Exhibit
     Number       Description of Document                        Page
     -------      -----------------------                        ----
      27.1        Financial Data Schedule.



















                                       10