Acute renal probability failure is not very common in childhood, but regarding its high mortality and morbidity, high probelility of it becoming chronic and cost, a true understanding of its etiologies and predisposing factors is fundamental for prevention and management. During a.16 month period, all children, 1 month to 15 years old with final diagnosis of acute renal failure were evaluated for predisposing factors (diarrhea, vomiting, hemorrhage, drugs, infectious diseases etc) and urinary indices. Diagnosis of acute renal failure was made on the basis of rising BUN and creatinine and eventually by exclusion of chronic renal failure. Etiologies of acute renal failure were determined by history, physical findings, laboratory data, imaging studies, urinary indices and in some cases by kidney biopsy. Fifty children, 37 boys (74%) and 13 girls (26%) with final diagnosis of acute renal failure were evaluated. Their age range was 3 months to 15 years, (6.29±4.76). They were categorized into 5 major groups. In order of frequency, they were tubulointerstitial diseases 18(36%).pre-renal 14 (28%), glomerular 13(26%). Hemolytic uremic syndrome 4(8%), and obstructive (2%). Nephrotoxic drugs were the major cause of ATN in this study. Many different factors may give rise to acute renal failure of "which, a majority of them are preventable. Appropriate fluid therapy in dehydration, avoidance of nephrotoxic medications and frequent monitoring of in-patient renal function, especially in intensive care units are some of the fundamentals of prevention.