Within 3 weeks of beginning continuous daily isoniazid and rifampin therapy for pulmonary tuberculosis, a patient developed acute renal failure. Renal biopsy demonstrated lesions characteristic of rapidly progressive glomerulonephritis with minor interstitial changes. Prior reports have emphasized the tubular and interstitial lesions associated with intermittent or discontinuous rifampin therapy for tuberculosis. This report documents the occurrence of severe glomerular pathology associated with continuous, daily antituberculous therapy. The spectrum of renal lesions occurring during antituberculous therapy, particularly in association with rifampin, may be wider than previously suspected.