Sixteen patients (12 male and 4 female, age 2-46 years) with endomyocardial biopsy-proven myocarditis were prospectively evaluated with immunosuppressive therapy including azathioprine and prednisolone in addition to other standard measures. Patients were either in NYHA class IV (n = 12) or class III (n = 4). Twelve patients showed improvement and the remaining 4 continued to deteriorate: 2 died at 1 and 2 months after therapy and the other 2 were lost to follow-up after 4-6 weeks of therapy. Three of the 12 patients who showed significant improvement, after sudden omission of therapy (at 8 weeks, 6 and 8 months) worsened and died. One patient who showed significant improvement died suddenly after 9 months of therapy while playing football. The remaining patients have shown significant clinical and haemodynamic improvement with normalization of myocardial morphology. Serial haemodynamic studies revealed a significant fall in cardiothoracic ratio (before: 62.3 +/- 4.7%; 3 months: 55.1 +/- 3.1%, P less than 0.0001; 6-12 months: 50.6 +/- 1.5%, P less than 0.0001), mean pulmonary artery pressure (before: 34.3 +/- 13.05 mm; 3 months: 20.4 +/- 8.71 mm, P less than 0.01; 6-12 months: 20.0 +/- 2.75 mm, P less than 0.01) and mean pulmonary artery wedge pressure (before: 26.0 +/- 9.07 mm; 3 months 14.0 +/- 5.63 mm, P less than 0.001; 6-12 months: 13.2 +/- 4.57 mm, P less than 0.001). The left ventricular ejection fraction improved from 24.3 +/- 8.36% to 35.8 +/- 9.72% (P less than 0.001) at 3 months and 49.8 +/- 18.2% (P less than 0.0001) at 6-12 months of therapy. Two patients have been subsequently lost to follow-up whereas the remaining 6 patients are on follow-up for 1-4 years after therapy and are doing fine. Our uncontrolled observations suggest that immunosuppressive therapy may be useful in patients with inflammatory myocarditis.