We conducted a retrospective cohort study to determine the influence of crack cocaine use on the outcomes of HIV infection. The use of crack cocaine was associated with an increased incidence of AIDS: 27.8 per 100 person-years versus 6.6 per 100 person-years for nonusers, adjusted hazard ratio = 3.8 (1.9-7.5), P < 0.001. More specifically, crack users had a greater incidence of disseminated histoplasmosis, pneumocystosis, pulmonary tuberculosis, bacterial pneumonia, oesophageal candidiasis, cerebral toxoplasmosis, salmonellosis, and genital herpes. The care of HIV-infected crack users is particularly challenging and requires additional efforts to reduce the high morbidity of these patients.