In order to examine differences in the prevalence of AIDS-defining conditions by race/ethnicity, we analyzed U.S. surveillance data for 203,470 adolescents and adults diagnosed with AIDS from 1988 through 1992. A number of AIDS-indicator conditions were more common among certain racial/ethnic groups. The prevalence of extrapulmonary tuberculosis was higher among blacks, Hispanics, Asians/Pacific Islanders, and American Indians/Alaskan Natives than among whites. The prevalence of isosporiasis and toxoplasmosis was higher among Hispanics than among blacks or whites. Furthermore, the likelihood of being diagnosed with extrapulmonary tuberculosis (TB), toxoplasmosis, or isosporiasis was generally higher among foreign-born than among U.S.-born persons of all racial/ethnic groups. The prevalence of all malignancies was higher among whites than among blacks or Hispanics. However, the magnitude of prevalence differences by race/ethnicity was reduced when we controlled for other demographic and exposure risk categories. Although race/ethnicity was significantly associated with the prevalence of a number of conditions, the relative frequency and patterns of AIDS-indicator conditions in different populations are probably most influenced by differences in (1) underlying prevalence or exposure to various etiologic agents causing these conditions, (2) diagnosis and reporting of conditions, and (3) access to care and therapy for HIV-related conditions.