We report a case of IgA nephropathy with renal failure in which the deterioration of renal function was inhibited by the addition of angiotensin II receptor blocker (ARB) losartan. Before administration of losartan, the mean decline in the patient's glomerular filtration rate (GFR) was 0.64 ml/min/1.73 m2/month. Losartan treatment was started when serum creatinine rose above 4.0 mg/dl. With this treatment the serum creatinine level has remained stable for 3.5 years, and the mean decline in GFR was 0.06 ml/min/1.73 m2/month. We document successful retardation of renal failure with the use of losartan. Our experience suggests that dialysis therapy can be delayed significantly in patients using this drug.