Polymerase Chain Reaction (PCR) allows the amplification of specific segments of Human Immunodeficiency Virus (HIV) genome. This technique is of interest for direct detection of HIV-1 DNA sequences in peripheral blood mononuclear cells. In our study, 54 out of 55 HIV-1 seropositive subjects were found positive with PCR assay. No detection of HIV DNA was observed in 36 seronegative at risk subjects (16 homosexuals and 20 polytransfused haemophiliacs), in 20 subjects with isolated and persistent anti-core antibodies, in 20 thalassemic polytransfused children and in 74 HIV seronegative blood donors (negative controls). These results are consistent with those of classical HIV serology and indicate that latent HIV-1 infection in seronegative at risk subjects is not a frequent event, if it exists.