The polymerase chain reaction (PCR) for human immunodeficiency virus type 1 (HIV-1) DNA was performed on specimens from 197 homosexual and bisexual men enrolled in studies of HIV-1 infection. Thirty cycles of amplification were conducted, followed by detection with probes corresponding to two gag primer pairs (SK 38/39 and SK 101/145). Of 107 men who were HIV-1 antibody-negative, 105(98%) were PeR-negative. Two who were initially PeR-positive antibodynegative were PCR- and antibody-negative on repeat testing of both the same specimen and specimens drawn 8–10 months later; this suggests that the first PCR results were false-positive. Of 90 men who were antibody-positive, PCR was positive in 87 (97%), including all 13 with AIDS, all 22 with AIDS-related conditions, all 11 with generalized lymphadenopathy only, and 41(93%) of 44 without signsor symptoms of HIV-1 infection. On repeat testing, all 3 PCR-negative, antibodypositive men were PCR-positive. In this population and with this technique, PCR had excellent agreement with the HIV-1 antibody test.