.
                                                                               .
                                                                               .

                                                                      EXHIBIT 21

                       SUBSIDIARIES OF ACMAT CORPORATION

     Listed are the subsidiaries of ACMAT Corporation:

<Table>
<Caption>
                                                                             STATE OF
NAME                                                          OWNERSHIP    INCORPORATION
- ----                                                          ----------   -------------
                                                                     
ACMAT Companies, Inc. ......................................     100%        Delaware
AMINS, Inc. ................................................     100%      Connecticut
Geremia Electric Co. .......................................     100%      Connecticut
ACSTAR Holdings, Inc. ......................................     100%        Delaware
ACSTAR Insurance Co.(1).....................................     100%        Illinois
ACMAT of Texas, Inc. .......................................     100%        Delaware
United Coastal Insurance Company(2).........................      66%        Arizona
</Table>

- ---------------

(1) Owned 100% by ACSTAR Holdings, Inc.

(2) Owned 66% by ACMAT Corporation and 34% by ACSTAR Insurance Company

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