The opportunistic infections, malignancies, and causes of death related to acquired immunodeficiency syndrome (AIDS) are changing, perhaps as a result of improved treatment, prophylaxis, and education. With its high percentage of persons who acquired the human immunodeficiency virus from intravenous drug (IVD) use, the population of patients with AIDS in the Bronx is potentially unique. All of the 257 consecutive adult human immunodeficiency virus and/or AIDS cases from two Bronx teaching hospitals from 1982 through 1995 were collected. The reports were reviewed for patient demographics, opportunistic infections, malignancies, and causes of death. One hundred thirteen cases from 1982 through 1988 were compared with 144 cases from 1989 through 1995, separated by the institution of antiretroviral therapy and Pneumocystis carinii (PCP) prophylaxis in the latter period. Male homosexuality as a risk factor significantly decreased from 24.8% of the cases in our study from the 1982/88 period to 12.5% during the 1989/95 period (P = 0.014), but IVD use cases showed no change. Cases of AIDS in heterosexual patients increased from 23.9 to 36.1% (P = 0.041) but did not achieve statistical significance unless the unknown risk category (a population shown to be infected predominantly through heterosexual transmission) was included. The prevalence of PCP at autopsy as an opportunistic infection decreased from 37.2 to 25% (P = 0.04), and its prevalence as a cause of death decreased from 31.9 to 13.9% (P = 0.007). This decrease was seen in the homosexual and heterosexual populations but not in the population of IVD users. The homosexual population, as opposed to the population of IVD users, may have taken greater advantage of PCP treatment and prevention. As a result, bronchopneumonia, not PCP, is now the leading cause of death among the patients with AIDS in this study. These findings have important implications for therapy and prophylaxis to control the spread of AIDS and its related infections, particularly in an inner city population troubled by drug use and poverty.