Due to lack of structured epidemiological studies, the incidence of acute renal failure (ARF) cannot be established in France. An empirical approach method based on answered questionaire sent by mail to nephrology centers affiliated or not to universities has been used to estimate the frequency of ARF requiring dialysis in 1991. We postulated that the French population was homogenously distributed among the different regions and that the response rate of 74% could be extrapolated to 100%. We could therefore calculate an incidence of 64 ARF per million of inhabitants. However, this underestimates the exact incidence since the acurate evaluation of IRA in a controled region (Champagne-Ardenne) is 104 per million of inhabitants. In addition, this study underlines the fact that many ARF are not treated in nephrology units, especially those associated with multiorgan failure requiring slow continuous hemofiltration and hemodialysis. It is suggested that the establishment of a national Registry for ARF and an adequate training of nephrologists are prerequisites to assess epidemiology and the global cost of ARF.