Three episodes of acute renal failure, all of them requiring hemodialysis, were observed in two patients. The renal biopsy specimens showed a massive periglomerular granulomatosis with crescentic glomerulonephritis. With cyclophosphamide therapy, a dramatic improvement in renal function was observed in both patients. Although the histologic findings and the response to cyclophosphamide therapy were characteristic of Wegener's granulomatosis, there was no evidence of respiratory involvement or extrarenal manifestations throughout the patients' clinical course. We think that these cases could represent limited forms of Wegener's granulomatosis with exclusive renal involvement.