In order to characterize the features of peripartum cardiomyopathy, clinical, echocardiographic and right ventricular endomyocardial bioptic data obtained from 6 patients (pts) (age range: 34.1 +/- 5.5. yrs) who fulfilled peripartum cardiomyopathy diagnostic criteria, were analyzed. Five of these pts had clinical and non-invasive studies for a mean period of 41.6 +/- 59.6 months. All but one were multiparous. Five developed heart failure one month before delivery. Three patients had active myocarditis at endomyocardial biopsy and were treated with immunosuppressive therapy. At follow-up, 3 pts improved by two or three grades of the NYHA functional classification. All 3 showed a reduction in the left ventricular end diastolic diameter (from 3.9 +/- 0.4 to 3.4 +/- 0.3 cm/m2) and a normalization of the shortening fraction in 2 (from 15 to 36% and from 13 to 46% respectively) at echocardiography. These two patients had active myocarditis at the first endomyocardial biopsy. At follow-up, all 3 pts with active myocarditis showed histological evidence of healed myocarditis. In conclusion, peripartum cardiomyopathy is characterized by a high incidence of active myocarditis and improvement seems more frequent in this subgroup of pts.