We studied the incidence of referral for treatment of end-stage renal disease (ESRD) in the Kaiser Foundation Health Plan (KFHP) in northern California from 1972 through 1977. In this population of over 1 million persons, we found an age-adjusted annual incidence of 44.9 per million after 1973, when the Federal ESRD Program went into effect. Age-specific incidence was highest in in men greater than 70 years of age and in women in the 50- to 59-year age group; the male/female ratio was 1.4:1. The most common diagnoses of patients referred with ESRD were glomerulonephritis (11.4 per million per year), diabetic nephropathy (5.0 per million per year), primary hypertensive disease (3.1 per million per year), and polycystic kidney disease (2.4 per million per year). Estimated rates of referral for ESRD were highest for Blacks, lowest for Whites, and intermediate for Asians. Incidence varied by geographic area within the health plan service area and was highest where the percentage of the Black population was highest.