PIP: Autopsies were performed by the cardiac pathology laboratory of 74 of 100 consecutive AIDS patients who died in Puerto Rico. The 32 with cardiac pathology are reviewed here. There were 27 males and 5 females, averaging 33 years old. 84% were heroin users and/or homosexual, and of the remaining 16%, 2 had heroin users and/or homosexual, and of the remaining 16%, 2 had received blood transfusions. The immediate cause of death was either respiratory or nervous system failure. One case of pericardial effusion (300 ml) associated with pleural effusion and ascites was found, but it was not clinically evident. 6 had cardiomegaly defined by cardiac mass 350 gm in males or 300 gm in females. There were no EKG findings other than sinus tachycardia with occasional ventricular premature beats. The most common pathological finding was nonspecific myocarditis. There were 5 cases with histoplasma showing cardiac foci of histiocytes, 3 with cardiac toxoplasma foci, 3 with mycobacterium granulomas in the myocardium or pericardium, 2 with cytomegalovirus myocarditis with intranuclear inclusions, 2 with cryptococcus neoformans, and 1 with atypical mycobacteria in the myocardium. 2 additional patients had coagulation necrosis of myocardial fibers. These results indicate that myocarditis is common in AIDS patients in Puerto Rico, especially in intravenous heroin users, and its causes are multiple. The clinical picture in terms of congestive heart failure or arrhythmias, however, is silent.