The clinical and epidemiologic characteristics of the acquired immunodeficiency syndrome (AIDS) were studied in a tropical area of Brazil. During an 18-month period (July 1989–January 1991), 111 consecutive AIDS patients (102 men and nine women) were evaluated. Patients reported homosexual/bisexual activities (60%), intravenous drug use (19%), or both (6%), heterosexual activities (11%), blood transfusions (2%), and 2% belonged to an undetermined category. Weight loss, fever, oral thrush, and diarrhea were present in ≥ 70% of the patients at presentation. An unexpected high frequency of hepatomegaly (49%) was detected, and found to be significantly associated with tuberculosis (P < 0.0001). Although the epidemiologic features of human immunodeficiency virus transmission were comparable to the United States/European pattern, the clinical spectrum of opportunistic infections more closely resembled that reported in Africa and Haiti, with a greater frequency of fungal and mycobacterial infections than Pneumocystis carinii pneumonia and viral infections.