Dilated cardiomyopathy (DC) and myocarditis (MCD) are still cardiac diseases of unknown etiology and pathogenesis. Due to uncertain natural history of MCD also treatment remains controversial. We observe long-term outcome of 30 pts with biopsy-proved MCD (group I) and 25 pts with DC (group II). The diagnosis of MCD was established on Dallas criteria of MCD. Almost all pts presented symptoms of congestive heart failure. All group I pts were treated with immunosuppressive agents: azathioprine 1.5 mg/kg/d and prednisone with initial dose of 1.5 mg/kg/d. After tapering off 0.75 mg/kg/d of prednisone and initial dose of azathioprine were given up to 6 months. All pts obtained digitalis, diuretics, ACEI, antiarrhythmic drugs if necessary. We studied the survival and clinical status (NYHA class) of treated pts. Clinical improvement was observed in 93% of pts with MCD within 6 months, but 20% of pts deteriorated within the next 6 months. Almost all pts survived 1 year. Out of 30 pts with MCD, 16 pts remain in lower NYHA class (NYHA I-II) between 26 and 69 months of follow-up. Within the group II (DC) 28% of pts died in the first year of observation. Out of 15 pts in 14 pts advanced chronic heart failure (NYHA III-IV) is presented in the end of observation. Echocardiographic parameters of pts with congestive heart failure and biopsy-proved MCD or DC did not differ significantly. We observed correlation between improvement of the LV echocardiographic parameters and improvement of clinical status of treated pts.