Four cases of myocarditis from toxoplasma gondii were observed at autopsy among 18 consecutive cases of acquired immunodeficiency syndrome (AIDS). All cases showed spotty inflammatory myocardial infiltration, consisting mainly of T lymphocytes and, to a lesser extent, of B lymphocytes, histiocytes, mastocytes and eosinophilic granulocytes, with presence of toxoplasma gondii in the cytoplasm of a few myocardial cells. The incidence of toxoplasmic myocarditis in heart involvement in AIDS was 22% in our cases, manifold higher than in preceding reports from the literature. This suggests that cardiac toxoplasmosis is far from rare in patients with AIDS.