The reverse transcriptase (RT) assay for human immunodeficiency virus (HIV) is tedious, expensive, and nonspecific for HIV activity. Because the Retro-Tek viral capture assay (VCA) (Cellular Products, Inc., Buffalo, NY) is relatively quick, inexpensive, and specific for HIV antigens, we compared the sensitivity and specificity of the two assays in a blinded fashion to see if the VCA could replace the RT assay. Specifically, peripheral mononuclear cells were cocultured from 11 Western blot-positive acquired immunodeficiency syndrome (AIDS) patients. The culture supernatant fluids were tested every 4-7 days for at least 28 days by VCA for HIV antigens, and by RT assay for retrovirus activity. Ten seronegative healthy donors with no risk factors were also cocultured and tested. Seven (64%) of 11 AIDS patients were positive by VCA and confirmed by RT assay in each instance. Concordance between VCA and RT assay was 100% in each patient. Time-to-positive detection was 7-28 days for both assays. Once a culture became positive by either assay, subsequent culture supernatant fluids remained positive by both assays until the culture was discarded, usually at day 28. The ten healthy seronegative donors were negative by both assays. These results suggest that the VCA is preferable to the RT assay for detection of HIV.