The nature, prevalence, functional significance, and indeed existence of myocardial disease in progressive systemic sclerosis (PSS) has been debated. In this study the clinical and pathological features of 52 autopsied patients were analyzed in an attempt to resolve these questions. A distinctive focal myocardial lesion ranging from contraction band necrosis to replacement fibrosis throughout both ventricular walls was present in 23 patients who had widely patent extramural coronary arteries. There were no morphologic abnormalities of the intramyocardial coronary arteries to account for these lesions. Comparing those patients having severe (13), mild (10), or no (24) PSS myocardial lesions, and patent extramural coronary arteries, there were no major differences in age, sex, frequency and severity of pulmonary, renal or hypertensive disease which could account for the myocardial necrosis and fibrosis. The three groups did differ, however, with regard to clinical cardiac abnormalities: ventricular arrhythmias and conduction disturbances were six and two times as frequent, respectively, in those with severe myocardial PSS compared to the other two groups. A pattern of primary myocardial disease with intractable congestive heart failure resulted from severe myocardial PSS in four patients, angina pectoris with normal coronary arteries was associated with the severe myocardial lesion in three patients, and sudden death in five. The occurrence of contraction band necrosis suggests that the myocardial damage in PSS might be due to intermittent vascular spasm of the type recognized in the digits and possibly kidneys and lungs, i.e., an intramyocardial Raynaud's phenomenon. The findings in our patients clearly show that myocardial progressive systemic sclerosis is a distinct entity with relatively frequent occurrence which may lead to arrhythmias, congestive heart failure, angina pectoris with normal coronary arteries and sudden death.