A 28-year old male was admitted to our hospital because of heart failure, chronic renal failure and nephrotic syndrome. Light microscopic findings of his kidney biopsy showed proliferation of mesangial cell and marked narrowing the lumina of small arteries and arterioles. The changes of these small vessels were not those of typical vasculitis, when we considered his age and his past history. The diagnosis of dilated cardiomyopathy was made by the findings in echocardiography and cardiac catheterization. Since the heart failure and renal disease seemed to be simultaneous initiated, it was supposed that the diseases in two organs were caused by a common pathogenesis related to that of vasculitis. When steroid pulse therapy was adopted, both of cardiac and renal function responded to this treatment (ejection fraction from 26% to 52%, creatinine clearance from 48 to 62 ml/min). Increase of CD56 positive cells (natural killer cells) in peripheral blood was ameliorated after the treatment. These findings suggest that cellular immunity may be concerned with the pathogenesis of the combination of dilated cardiomyopathy and renal disease in this case.