The virological diagnosis of HIV infection in pregnant women mainly consists of detecting antibodies to structural viral antigens. The difficulty lies more in the interpretation of the confirmatory assay than in technical problems. The result is critical since the continuation or interruption of pregnancy is dependent upon it. The diagnosis of HIV infection in newborns has been hampered by the presence of passively acquired maternal antibodies. The diagnosis at birth therefore must include culture of peripheral blood mononuclear cells for virus isolation and detection of serum antigen. However, due to the difficulty or lack of sensitivity of these tests new diagnostic procedures, such as the polymerase chain reaction, must be developed to improve the accuracy of the early diagnosis. Such new approaches must be evaluated very carefully before being introduced in routine diagnosis.