The influence of human immunodeficiency virus (HIV) infection and vaccination schedule on the immunogenicity of a hepatitis A vaccine was examined. Ninety HIV-infected homosexual men received two vaccinations with hepatitis A vaccine (each 2 mL of 720 ELISA units/mL) either 1 or 6 months apart; 44 HIV-uninfected men received vaccine at study entry and at 6 months. Anti-hepatitis A virus (HAV) titer after vaccination was measured in 83 HIV-positive and 39 HIV-negative men. Seroconversion (anti-HAV antibody > or = 20 IU/L) after two vaccinations occurred more frequently in HIV-negative men (100% vs. 88.2%; P = .03). Anti-HAV titer after two vaccinations was also significantly greater in HIV-negative men (1086 vs. 101 IU/L; P = .0001). HIV-positive men who responded to vaccination had significantly more CD4 lymphocytes (mean, 540/microL) at baseline than those who did not (280/microL; P = .033). Vaccine schedule did not affect response. Vaccination of susceptible patients against HAV should be recommended early in HIV infection using the shorter course to encourage compliance.