Patients are stratified into three groups. Fifteen patients previously immunized with MicroGeneSys rgp160 antigen in ACTG 137 and not on antiretroviral therapy will receive intradermal injections of Immuno-AG rgp160 IIIB (vero cell expressed) in one arm, followed 1 week later by intradermal injections of MicroGeneSys rgp160 IIIB (baculovirus expressed) in the opposite arm (stratum 1). Forty patients who are not previously immunized with rgp160 will receive intradermal injections of Immuno-AG gp160 IIIB in one arm simultaneously with MicroGeneSys gp160 IIIB in the opposite arm; these patients are either not on antiretroviral therapy (stratum 2) or currently on antiretroviral therapy (stratum 3). All patients return 48 hours after each injection for skin test reading.