In a prospective study, a commercial polymerase chain reaction (PCR) system was compared with a conventional procedure, based on PCR and hybridization with a radio-labeled probe, for the detection of human immunodeficiency virus (HIV) infection in 131 blood samples from 80 children born to HIV-seropositive mothers. Twenty-three of these children were HIV infected. The sensitivity and specificity of the commercial assay as compared with the conventional PCR procedure were 100% and 95.1%, respectively. This commercial method simplifies the performance of the conventional PCR technique and can be used to detect HIV type 1 vertical transmission.