We performed a retrospective review to evaluate the results of a nonsurgical approach to the management of primary vesicoureteral reflux during a 10-year period (1976 to 1986). During that interval patients with reflux were studied initially with a standard voiding cystourethrogram and either an excretory urogram or a renal scan with glomerular filtration rate and/or differential renal function determination. Height, weight, blood pressure, urine cultures and serum creatinine measurements also were obtained. Isotope cystography was used for followup examinations. A single, negative isotope cystogram was the radiological criterion for cessation of reflux. The charts of 545 children (55 per cent had bilateral reflux) with 844 refluxing ureters were reviewed. Based upon the international classification vesicoureteral reflux was grade I in 6.6 per cent of the cases, grade II in 54.2 per cent, grade III in 31.6 per cent, grade IV in 5.7 per cent and grade V in 1.9 per cent. All children were kept on long-term continuous prophylactic antibiotics and they were re-evaluated annually with isotope cystography. The followup rate for the entire group was 88 per cent. During the observation period spontaneous resolution of reflux was noted in 36 per cent of the patients and 39 per cent of the total refluxing ureters. Only 13 per cent of the entire group underwent surgical correction of reflux. Presently, 39 per cent (215) of the patients continue to be followed with reflux. Of the total group 66 patients (12 per cent) were lost to followup. In the 194 patients with spontaneous resolution of reflux the mean duration of reflux was 1.69 years, with 30 to 35 per cent resolving each year. Based on Student's t test there was a significant difference in duration of reflux in patients with grade II compared to grade III reflux (1.56 versus 1.97 years, p less than 0.04). When age at presentation was compared with duration of reflux there was a significantly shorter duration of reflux only in those patients presenting from age 0 to 12 months, compared to those 13 months and older (1.44 versus 1.85 years, p less than 0.02). Renal function was evaluated by serum creatinine, calculated glomerular filtration rate or differential diethylenetriaminepentaacetic acid scan results.(ABSTRACT TRUNCATED AT 400 WORDS)