A 71-year-old woman was admitted to our department because of acute myocarditis. She was ameliorated with conventional heart failure treatment, however she developed left ventricular dilatation and cardiac troponin T (cTnT) was elevated again to >1.0 ng/ml 6 month after the first admission. She was re-admitted because of recurrent decompensated heart failure in spite of conventional treatment. Right ventricular endomyocardial biopsy revealed active myocarditis. Immunosuppressive therapy with prednisolone and azathioprine improved her symptoms and left ventricular function accompanied by a striking decrease of cTnT levels. The decreased cTnT level indicated an effective response to immunosuppression early after the beginning of treatment. These findings suggested that it is possible to evaluate the response to immunosuppressive therapy by serial measurement of cardiac troponin.