A group of 39 girls with urinary tract infection are studied to analyse the clinical findings, response to treatment and natural history of the disease. All of them had more than three episodes of infection per year and renal function and initial cysto-urographic study were normal. Mean age at diagnosis was 4.8 years and the mean follow-up 3.4 years. In 7.6% of cases familial incidence was observed. During infection free periods, 35.8% of patients had urinary incontinence. 25% of recurrences were asymptomatic. Only one case developed during the follow-up a unilateral polar scar associated with grave II vesicoureteral reflux. Recurrence rate/girl/year, decrease from 3.8 during the first year to 1.5 at 5th year of follow-up. Patients who received prophylaxis with nitrofurantoin showed a clear decrease in rate of recurrence.