The 'gold standard' for the diagnosis of myocarditis is endomyocardial biopsy. Although the specificity of this invasive method is good, its sensitivity is questionable. Therefore, a non-invasive diagnostic method with greater sensitivity (even if it were overly sensitive) would constitute a useful screening tool for identification of patients who should undergo endomyocardial biopsy. Antimyosin immunoscintigraphy fits such a criterion since it is highly sensitive and specific for diagnosis of myocardial necrosis, which is one of the two obligatory components for the diagnosis of myocarditis. Therefore studies were performed on patients with clinical histories suggestive of myocarditis such as acute onset of dilated cardiomyopathy, myocarditis masquerading as acute myocardial infarction and patients presenting with unexplained life-threatening ventricular tachyarrhythmias. In all these studies, antimyosin imaging had higher sensitivity than endomyocardial biopsy for the diagnosis of myocarditis. A rationale is provided for the increased sensitivity and specificity of antimyosin immunoscintigraphy for diagnosis of myocyte necrosis associated with myocarditis, relative to endomyocardial biopsy.