Central nervous system disease due to Toxoplasma gondii is a common cause of morbidity and mortality in patients with the acquired immunodeficiency syndrome. Cardiac toxoplasmosis, however, has been described in only a limited number of cases. In a 45-gear-old patient with symptoms suggestive of myocarditis, Toxoplasma gondii was detected in myocardial tissue obtained by biopsy. After the institution of appropriate antiprotozoal therapy, the patient recovered. This patient is believed to be the first patient to survive biopsy-proven myocarditis caused by Toxoplasma gondii. Cardiac toxoplasmosis should be ruled out in HIV-infected patients presenting with high fever and/or cardiorespiratory symptoms and exhibiting serologic evidence of prior exposure to Toxoplasma gondii as determined by a positive IgG EIA, especially if the CD4+ count is low and no systemic Pneumocystis carinii pneumonia prophylaxis has been administered. A high index of clinical suspicion and, if necessary, invasive diagnostic tests, including myocardial biopsies, are most important in making the correct diagnosis.