Forty-two infants of HIV-seropositive women were evaluated to determine the value of polymerase chain reaction (PCR) in the early detection of HIV infection. All infants less than 6 months old had a simultaneous PCR and culture for HIV. There was an 88% concordance between the two techniques. PCR results showed an excellent correlation with clinical outcome; no PCR-negative patient has subsequently been found to be infected. Occasional false-positive or equivocal PCR results did occur. There was one false-negative culture. PCR is a rapid and sensitive diagnostic test for the early diagnosis of HIV infection in infants at risk, but at present it should be performed in conjunction with other diagnostic tests and good clinical follow-up.