Mortality in acute renal failure (ARF) still exceeds 50%. However, while the outcome data for ARF in adults are readily available, similar data for pediatric population are scarce. Children survival rate varies between centres, particularly in regard to age and size of a child, and cause of ARF. Dialysis continues to be a major supportive intervention in severe acute renal failure. There are few data available that address treatment modality impact on ARF outcome. The youngest patients are usually treated with peritoneal dialysis, though sometimes hemodialysis is used even in children with very low birth body weight. We reviewed a 9-year experience with hemodialysis in children under 5 years of age. 33 children (13 boys, 10 girls) were treated with hemodialysis in the analysed period. Their mean age was 26.8 +/- 23.0 years, mean body weight 10.6 +/- 4.6 kg. Cardiac surgery and haemolytic-uremic syndrome were the major causes of ARF in the studied group. Dialysis duration, ultrafiltration rate, maximum blood flow, mortality and its risk factors were analysed. 232 dialyses were conducted in the studied group, mean 6 dialyses per patient. Mean dialysis time was 85 +/- 42 min for the first and 135 +/- 38 min for consecutive procedures. Urea reduction rates in the first and following dialyses were 50% and 58% respectively. Maximum blood flow was 7.4 ml/kg/min, i.e. higher than recommended. However, no adverse events were caused by that. Mortality rate was 38%. Hemodialysis may be used in small children, when indicated, with no higher death rate than standard peritoneal dialysis.