We investigated chronic renal failure (CRF) in 166 Iranian children (95 boys and 71 girls) from July 1991 to June 1999. The mean age at onset of CRF was 7.9+/-4.5 years. The most common cause of CRF was congenital urological malformations (78 cases). The second most common cause of CRF was hereditary nephropathy (21%). Glomerular diseases accounted for only 10% of children who later went on to develop renal failure. High rates of cystinosis and primary hyperoxaluria were seen, and these elevated rates could be due to a high prevalence of parental consanguinity. Eighty-six patients required renal replacement therapy, of whom the majority underwent hemodialysis. The prevalence of primary reflux as a cause of CRF was high compared with reports from western countries. Earlier diagnosis and management of urinary tract infections in this group could reduce the prevalence of reflux as a cause of CRF in this population.