Heart failure due to myocarditis can be a devastating illness. At the same time, immunosuppressive therapy is associated with considerable risks of untoward side effects. Clinicians did not know whether, under what circumstances, or in what form, this hazardous treatment should be used in such critically ill patients. In addition, if immunosuppressive therapy was of benefit, then endomyocardial biopsy in patients suspected of having myocarditis was a justified procedure. The trial also provided information concerning the side effects of immuno-suppressive therapy in such patients.