Renal replacement therapy (RRT) remains the most important tool for all patients with end-stage renal disease (ESRD) in the world. Patients are usually listed in the national renal registries which report demographic data, incidence, prevalence and outcome. Differences in acceptance of the RRT, patient demographics, socioeconomic burdens and national health care legislature influence the validity of international comparisons of ESRD therapy. For this reason, the renal registries decided to organize an international collaborative study group, the International Federation of Renal Registries (IFRR), for improving the standardization of renal databases and for promoting international collaborative studies. Demographic data from renal registries in 1996 showed that approximately 1,000,000 of ESRD patients received RRT throughout the world and approximately 200,000 new patients started RRT. The different distribution of patients in the world is strongly influenced by the level of gross domestic product (GDP), since economical crisis may influence the number of patients starting RRT. The reported incidence and prevalence values of ESRD patients in RRT from the renal registries show these differences. The mortality rate of these patients is notably influenced by the percentage of enrolled diabetic RRT patients. Therefore, important differences in outcome of RRT depend on the underlying disease which is a determinant factor of prognosis. Other factors responsible for the outcome are represented by dialysis dose, type of membrane, erythropoietin and nutritional status.