We examined the incidence of treated end-stage renal disease (ESRD) among the two million members of the Kaiser Permanente Medical Care Program of Northern California from 1973 through 1985. The age-adjusted incidence rates rose from 33.9 to 81.7 per million person-years and showed no signs of stabilization. Rates were higher in men than in women and rose with age. Marked upward trends (p less than .001) in the rates of treated ESRD associated with diabetic nephropathy and hypertension were noted.