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                                FORM 10-K/A-1

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

x   ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
                                   ACT OF 1934


For the fiscal year ended December 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: 0-14950

                              Argonaut Group, Inc.

          (Exact name of Registrant as specified in its charter)

                               Delaware 95-4057601

(State or other jurisdiction of (I.R.S.  Employer incorporation or organization)
Identification No.)
                         250 Middlefield Road

                         Menlo Park, California    94025-3500
           (Address of principal executive offices) (Zip code)

                                 (650) 858-6600

(Registrant's telephone number including area code)

Securities registered pursuant to section 12(g) of the Act:

                               Title of Securities

Common Stock, par value of $.10 per share

        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 ____

        Indicate by check mark if disclosure of  delinquent  filers  pursuant to
Item 405 of Regulation S-K is not contained  herein,  and will not be contained,
to the best of  registrant's  knowledge,  in  definitive  proxy  or  information
statements  incorporated  by  reference  in Part  III of this  Form  10-K or any
amendment to this Form 10-K. |X|

As of  March  20,  2000,  registrant  had  22,157,756  shares  of  Common  Stock
outstanding,  and  the  aggregate  market  value  of the  voting  stock  held by
nonaffiliates was approximately $414.1 million.


                       DOCUMENTS INCORPORATED BY REFERENCE

Part II: Excerpts from Argonaut Group,  Inc.'s Annual Report to Shareholders for
the Year Ended December 31, 1999. Part III: Excerpts from Argonaut Group, Inc.'s
Proxy  Statement for the Annual Meeting of  Shareholders to be held on April 25,
2000.
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Reserves for Losses and Loss Adjustment Expenses

Incorporated  herein by reference is the information set forth under the caption
"Management's  Discussion  and Analysis of Results of  Operations  and Financial
Condition-Results  of  Operations"  in the  Annual  Report  to  Shareholders  of
Argonaut  Group for the fiscal  year ended  December  31,  1999 and in "Note 4 -
Reserves  for  Losses  and  Loss  Adjustment  Expenses"  in  the  Notes  to  the
Consolidated Financial Statements of the Annual Report. See Exhibit Index.

During the fourth quarter of 1999, the Company  increased  workers  compensation
loss  reserves  by  $31.7  million,  reflecting  higher  than  anticipated  loss
development  for  accident  years  1998 and 1999,  particularly  in  California.
Preliminary  indications  in the first  quarter of 2000 show  continued  adverse
development  of these  accident  years.  If these  trends  continue,  additional
strengthening of these reserves will be required.

Reserves  for  environmental  claims  were $91.3  million  and $96.3  million at
December 31, 1999 and 1998,  respectively.  Reserves  for  asbestos  claims were
$75.3 and $76.6 million at December 31, 1999 and 1998.

In the opinion of management, the Company's reserves for each of these liability
issues represent the Company's best estimate of its ultimate liabilities,  based
on currently  known facts,  current law,  current  technology,  and  assumptions
considered   reasonable   where  facts  are  not  known.   Due  to   significant
uncertainties  and  related  management  judgments,  however,  there  can  be no
assurance  that  future  loss  development,  favorable  or  unfavorable,  can be
accurately predicted.

The following  tables on page 8 and 9 indicate the manner in which  reserves for
losses and loss  adjustment  expenses at the end of a particular  year change as
time  passes.  The first  table  (Table I)  presented  is net of the  effects of
reinsurance. The second table (Table II) presented includes only amounts related
to direct insurance.

The first line  shows the  reserves  as  originally  reported  at the end of the
stated year. The second section shows the cumulative  amounts paid as of the end
of  successive  years  related to those  reserves.  The third  section shows the
original recorded reserves as of the end of successive years adjusted to reflect
facts and circumstances later discovered.  The last line,  cumulative deficiency
or  redundancy,  compares  the adjusted  reserves to the reserves as  originally
established  and shows that the  reserves  as  originally  recorded  were either
inadequate or excessive to cover the estimated cost of claims as of December 31,
1999.

Conditions  and trends that have affected the  development  of these reserves in
the past will not necessarily  recur in the future.  It would not be appropriate
to use this cumulative history in the projection of future performance.

                                                         Page 7


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Table I

        Analysis of Losses and Loss Adjustment Expenses (LAE) Development
          (in millions) (Net of Reinsurance) Amended 3/31/2000
<TABLE>
<CAPTION>
                        ---------------------------------------------------------------------------------------------------
                           1990       1991      1992       1993       1994      1995      1996     1997     1998    1999
                           ----       ----      ----       ----       ----      ----      ----     ----     ----    ----
<S>                       <C>        <C>       <C>        <C>         <C>       <C>       <C>      <C>      <C>     <C>

Reserves for Losses
and LAE (a)               $1,348.5   $1,287.8  $1,201.9   $1,107.6     $976.6    $858.1   $951.0   $884.0   $763.2  $706.5
Cumulative Amount
Paid as of: (b)
One year later               313.1      307.3     276.9      259.9      239.7     214.2    179.0    172.7    149.8
Two years later              537.5      525.8     489.2      444.7      417.9     356.2    309.7    278.7
Three years later            698.5      697.6     638.9      588.8      531.5     468.6    392.7
Four years later             835.7      821.4     759.5      684.1      623.9     537.9
Five years later             940.1      919.5     839.9      758.5      682.9
Six years later            1,021.3      991.0     906.8      814.8
Seven years later          1,082.7    1,051.3     962.7
Eight years later          1,134.2    1,106.0
Nine years later           1,182.6
Reserves Re-estimated
As of:

One year later             1,358.3   1,285.2    1,197.1    1,086.8      996.5   1,073.6    934.0    819.2    785.4
Two years later            1,356.9   1,311.9    1,202.0    1,083.0    1,180.8   1,038.9    895.5    851.1
Three years later          1,381.9   1,315.9    1,203.0    1,283.4    1,159.2   1,014.1    916.0
Four years later           1,374.1   1,325.9    1,403.1    1,277.3    1,152.5   1,033.8
Five years later           1,384.9   1,514.9    1,400.6    1,268.2    1,154.6
Six years later            1,572.0   1,524.3    1,396.2    1,262.2
Seven years later          1,575.6   1,518.8    1,391.3
Eight years later          1,572.8   1,516.7
Nine years later           1,570.9
Cumulative (Deficiency)
Redundancy: (c)           ($222.4)   ($228.9)  ($189.4)   ($154.6)   ($178.0)  ($175.7)    $35.0  ($32.9)  ($22.2)
</TABLE>

(a)    Reserves for losses and LAE, net of reserves for reinsurance.
(b)    Cumulative amount paid, net of reinsurance payments.
(c)    Represents changes of net reserves between the original estimate
       (for each accident year) of the indicated year and the reserve
       re-estimated as of the end of the current year.  Re-estimated reserves
       are calculated by adding cumulative amount paid to unpaid loss and LAE
       and  incurred  but not reported (IBNR) at year end for each accident
       year.

                                                         Page 8

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Table II

Analysis of Losses and Loss Adjustment Expenses (LAE) Development (in millions)
                                                  (Direct Insurance Only)
                                                     Amended 3/31/2000
<TABLE>
<CAPTION>

                      ------------------------------------------------------------------------------------------------------
                        1990       1991       1992      1993       1994      1995       1996      1997      1998     1999
                        ----       ----       ----      ----       ----      ----       ----      ----      ----     ----
<S>                    <C>        <C>        <C>       <C>        <C>       <C>        <C>        <C>       <C>     <C>
Reserves for Losses
and LAE (a)            $1,561.8   $1,494.4   $1,390.9  $1,284.1   $1,161.5  $1,026.1   $1,158.8  $1,063.2   $935.8   $897.4
Cumulative Amount
Paid as of: (b)
One year later            384.7      355.7      325.6     288.3      267.5     245.2      234.7     197.0    177.8
Two years later           656.2      621.6      564.4     499.3      474.8     437.8      389.3     329.6
Three years later         862.6      818.2      739.3     668.9      625.4     572.1      498.5
Four years later        1,023.5      965.1      884.2     787.9      737.5     665.5
Five years later        1,149.2     1,086.1     983.5     881.4      817.9
Six years later         1,252.8    1,174.5    1,069.3     951.1
Seven years later       1,327.6    1,253.6    1,134.2
Eight years later       1,396.5    1,314.3
Nine years later        1,450.8
Reserves Re-estimated
as of:
One year later
                        1,619.3    1,512.6    1,414.2   1,291.7    1,179.7   1,300.3    1,159.7   1,006.2    990.1
Two years later         1,645.8    1,570.2    1,448.8   1,278.8    1,423.1   1,282.8    1,134.3   1,069.7
Three years later       1,702.3    1,603.7    1,440.6   1,533.8    1,404.1   1,267.2    1,182.5
Four years later        1,719.7    1,604.2    1,694.5   1,526.6    1,412.1   1,317.3
Five years later        1,723.6    1,841.5    1,687.5   1,532.5    1,440.9
Six years later         1,956.8    1,850.4    1,698.0   1,546.4
Seven years later       1,958.8    1,859.5    1,708.6
Eight years later       1,970.0    1,869.4
Nine years later        1,980.8
Cumulative (Deficiency)
Redundancy: (c)        ($419.0)   ($375.0)   ($317.7)  ($262.3)   ($279.4)  ($291.2)      $23.7    ($6.5)  ($54.3)
</TABLE>


(a)    Reserves for losses and LAE, excluding effects of reinsurance.
(b)    Cumulative amount paid, excluding effects of reinsurance.
(c)      Represents  changes of direct  reserves  between the original  estimate
         (for  each  accident  year)  of the  indicated  year  and  the  reserve
         re-estimated as of the end of the current year.  Re-estimated  reserves
         are calculated by adding  cumulative amount paid to unpaid loss and LAE
         and  incurred  but not  reported  (IBNR) at year end for each  accident
         year.

                                                         Page 9

                                    SIGNATURE

Pursuant to the  requirements of Section 13 or 15(d) 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.

ARGONAUT  GROUP,  INC.
By /s/  James  B  Halliday
--------------------------
James B Halliday Vice
President and Treasurer

Date:  March 31, 2000

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