Between 1982 and 1986, 96 children with non-obstructive vesicoureteric reflux were included in a prospective study. Three patients withdrew from the study and results are therefore presented on 93 children with 135 refluxing ureters who were followed up for at least 5 years. Initially, all children with reflux grade III or less received antibiotic treatment only. Those with reflux grade IV were randomised to antibiotic treatment alone versus surgery plus antibiotic treatment; the primary treatment of reflux grade V was reimplantation. In 85 ureters treated by antibiotics only, reflux disappeared in 64 cases and was reduced in 12. In 50 ureters treated by reimplantation, reflux was cured in 46 cases and no severe ureteric obstruction was seen. Conservative management of reflux grade IV was less successful than surgery. The results of conservative, non-surgical treatment of reflux grades I-III were satisfactory, but for grades IV and V surgery should be the treatment of choice if detrusor instability has been excluded.