From 1978 through 1984, the incidence of treated end-stage renal disease (ESRD) secondary to diabetic nephropathy increased from 3 to 19 per million population among the membership of the Kaiser Permanente Medical Care Program in Northern California. Forty-eight percent had type II diabetes. Among 66 type II diabetics retinopathy was less severe and hypertension was more frequent than among 50 type I diabetics. Blacks were represented in a higher proportion than expected from their proportion of the health plan membership. Among type II diabetics who developed ESRD, once proteinuria occurred, nephropathy progressed at the same rate observed in type I diabetics. This observation suggests that the clinical progression of diabetic nephropathy may be similar for both types of diabetes after the development of proteinuria, but requires prospectively collected data for confirmation.