To examine the possible relationship between cardiac and skeletal muscle disease in systemic sclerosis, we reviewed computerized records of 1095 consecutive patients with systemic sclerosis. One hundred eighty three (17%) had skeletal myopathy. Thirty-nine (21%) of the 183 fulfilled criteria for myocardial disease, compared with 90 (10%) of the 912 without myopathy (p < 0.0001.) Nineteen (10%) of the 183 had clinical CHF compared with 38 (4%) of the remainder (p < 0.002.) Fifteen (8%) of the patients with myopathy died of cardiac causes compared with 27 (3%) of the 912 without myopathy (p < 0.002.) Twenty-five patients with coexistent myopathy and myocardial disease, in the absence of other identifiable contributing causes, were identified. This group was characterized by a high incidence of cardiac conduction abnormalities (60%) and by the severity of the myocardial dysfunction and arrhythmias, both atrial and ventricular that they experienced. Eighteen of these 25 patients died; 12 (67%) died suddenly. Eight of the 18 (44%) had intractable CHF, which directly contributed to their deaths. Myocardial fibrosis was the predominant histologic abnormality at autopsy. However, autopsy of a patient who died in the context of acute "myocarditis" showed severe myocytolysis with contraction band necrosis but without inflammation or fibrosis; this is consistent with possible ischemically mediated injury. We conclude that skeletal and cardiac muscle disease in systemic sclerosis are associated. Patients with myopathy are at increased risk for CHF, sustained symptomatic arrhythmias, and cardiac death, particularly sudden death.