Twenty patients with necrotizing glomerulonephritis were seen at a general teaching hospital over a 6-year period. These patients represented 5.2% of the histologically verified glomerulonephritis population. Twelve patients had an associated systemic illness (vasculitis in 6, Wegener's granulomatosis in 2, Goodpasture syndrome in 2, infective endocarditis in 1, pulmonary renal syndrome in 1). The clinical course was variable, with equal numbers of patients having rapidly progressive and indolent courses. Four patients (20%) had less than 10% normal glomeruli on renal biopsy and developed end-stage renal failure. Although immunosuppressive and anticoagulant therapy was associated with an improvement in renal function, 6 patients (30%) had died after a mean follow-up period of 25 months.