In order to assess the incidence of chronic renal failure (CRF) and the demographic characteristics of affected patients, a prospective, multicenter epidemiologic study was conducted with the cooperation of all nephrology and dialysis units in the Ile-de-France district, the total population of which is 10660000 inhabitants (source: national census, march 1990). Included were patients with a plasma creatinine (Pcr) concentration > or = 200 mumol/l referred during the one-year period from July 1, 1991 until June 30, 1992. The overall response rate was 98.5%. A total of 2775 adult patients were recorded, including 1780 males (64%) with a mean (+/- SD) age of 58.1 +/- 16.3 years and a mean Pcr of 447 +/- 214 mumol/l, and 995 females (36%) with a mean age of 59.2 +/- 16.4 years and a mean Pcr of 425 +/- 185 mumol/l. Age of patients was < 40 in 16%, 40-59 in 31%, 60-74 in 34% and > or = 75 years in 19%. Pcr was 200-399 mumol/l in 54%, 400-599 mumol/l in 25%, 600-799 mumol/l in 12% and > or = 800 mumol/l in 9%. The overall incidence of CRF was 260/million population/year, twice higher in males than in females (348 vs 179/10(6)/year, p < 0.001). Incidence of CRF dramatically rose with age in both genders, with figures as high as 1124 and 356/10(6)/year respectively in male and female patients aged > or = 75 years, vs 288 and 151/10(6)/year in patients aged < 40 years. A sequential evaluation was performed in a representative sample of 251 patients with initial Pcr > or = 300 mumol/l. End-stage renal failure (ESRF) was reached within one year in 99% of patients with PCr > 600, 49% with Pcr 500-599, 24% with PCr 400-499 and 11% with PCr 300-399 mumol/l. Based on these figures, the predicted incidence of ESRF within one year of referral was 864 out of the 2775 patients, an estimated annual incidence of 81 patients per million population. In conclusion, this prospective study affords the first direct information on the incidence of chronic renal failure and the demographic characteristics of patients with CRF in the Ile-de-France district. Due to the design of the study conducted only in nephrology units, the estimated figure of 81 new patients per million population per year reaching ESRF is a minimal evaluation. In view of the relentless aging of population in France, an incidence of at least 100 ESRF patients per million population per year is to be expected in the next future.