Three methods (IVAP, p24 antigenemia and viral cultivation) for the diagnosis of HIV-1 infection among children born to HIV-1 infected mothers were prospectively evaluated to determine the applicability of IVAP as a useful technique for that purpose. We tested 15 children (8 p0 and 7 pII) and 19 adults with well-established serological status for HIV infection. The children were followed for at least 1 year, unless tbey developed symptoms of clinical AIDS, or their HIV serology became negative. The IMP method was more sensitive and specific than the other 2 tests in determining whether or not the infants were infected with HIV. All negative test results (5/8) were confirmed during the follow-up period, while two-thirds of the IVAP positive children developed AIDS during the same time period. Despite the small sample studied, we conclude that IVAP is an inexpensive and simple technique potentially useful to establish whether or not HIV-seropositive children born to infected mothers are HIV infected.