This study analyzes morphologic and functional alterations detected by M-mode and 2-dimensional echocardiography in 41 patients with histologically proven myocarditis and different clinical presentations: congestive heart failure (63%), atrioventricular block (17%), chest pain (15%) and supraventricular arrhythmias (5%). Left ventricular dysfunction was common (69%), particularly in patients with congestive heart failure (88%), often without or with minor cavity dilatation. Patients with atrioventricular block or chest pain had usually preserved ventricular function. Right ventricular dysfunction was present in 23%. Additional findings included asynergic ventricular areas (64%), left ventricular "hypertrophy" sometimes reversible (20%), hyperrefractile myocardial areas (23%), ventricular thrombi (15%) and "restrictive" ventricular filling (7%). It is concluded that echocardiographic features of myocarditis are polymorphous and nonspecific. The echocardiographic pattern can simulate alternatively dilated, hypertrophic, restrictive or "right" ventricular cardiomyopathy, as well as coronary artery disease. In an appropriate clinical context, echocardiography can be helpful in the diagnosis of myocarditis and in the selection of patients for endomyocardial biopsy.