A prospective study of antibody production by adults infected with human immunodeficiency virus (HIV) after vaccination with T lymphocyte-dependent diphtheria toxoid, tetanus toxoid, and inactivated trivalent poliovirus vaccine was conducted. Individuals were divided into three groups according to CD4+ T-lymphocyte count: group 1 had a count of < or = 100-300 x 10(6)/L; and group 3, > 300 x 10(6)/L. After vaccination, 61%, 70%, and 73% of the individuals in groups 1, 2, and 3, respectively, developed protective titers of antibody to diphtheria toxin; the mean postvaccination antibody titer of HIV-infected individuals was significantly lower than that of healthy controls not infected with HIV. Furthermore, the mean titers of antibodies to tetanus toxin and poliovirus were significantly lower in HIV-infected individuals with CD4+ lymphocyte counts of < 300 x 10(6)/L than in controls. Of the HIV-infected vaccinees, 83%-100% were protected against tetanus and 78%-100% against polio. We conclude that HIV-infected individuals with CD4+ lymphocyte counts of < 300 x 10(6)/L have an impaired (secondary) antibody response after receipt of T lymphocyte-dependent vaccines.