We reviewed the records of patients with genitourinary tumors that had been diagnosed and treated at the Section of Pediatric Surgery of Marqués de Valdecilla Hospital from 1974 to 1990. There were 14 such tumors. Of these, 12 (85.7%) were Wilm's tumor. This tumor type is the subject of the present study. Regarding its clinical features, 33.3% of the cases consulted for hematuria and an abdominal mass was the most common finding in the course of the disease (83%). We underscore the usefulness of CT and ultrasound in making the diagnosis. In the cases where these noninvasive imaging techniques were used, their efficacy rate was 100%. Together with IVP, these constitute the fundamental diagnostic tools. With regard to treatment, radical nephrectomy was performed in all cases and combined with radio and chemotherapy according to protocol. Pathological examination confirmed the diagnosis of Wilms' tumor in all the cases. Following the NWTS classification, there were 2 stage I,5 stage II, 2 stage III and 3 stage IV. Apart from tumor stage, the histological features significantly influenced the diagnosis. The survival rates for those with favourable or unfavourable histologic features were 70% and 36%, respectively.