Observations over 2 to 14 months in 19 adults with various unrelenting renal diseases considered to have immunological basis suggest that azathioprine (Imuran) combined with high doses of prednisone may have value in treating certain of these disorders. Good results occurred in steroid-resistant or steroid-intolerant nephrotic syndrome, particularly with minimal pathological glomerular changes. In lupus nephritis, the condition of three of four patients improved when steroids alone had been ineffective. In subacute and chronic glomerulonephritis a few patients experienced improvement, but the condition of most was unchanged or worse. Where steroidal side effects were a problem, azathioprine allowed a reduction or discontinuance of steroids, with continuing favorable results. Hematological and gastrointestinal symptoms were the major side effects encountered, and were not severe except in patients with advanced renal failure.