The occurrence of renal insufficiency associated with heavy glomerular proteinuria during the course of continuous rifampin therapy in a patient with pulmonary tuberculosis is reported. Renal biopsy demonstrated acute interstitial nephritis, normal glomerular histology, effacement of glomerular epithelial cell foot processes, and electron-dense deposits in mesangial matrix and subendothelial and paramesangial sites. Discontinuation of rifampin was followed by improvement in renal function and abatement of proteinuria. We call attention to the broad clinical and morphologic spectrum of nephrotoxicity which may be induced by rifampin and a variety of other drugs.