Four patients out of 23 girls and 7 boys who were treated by successful ureteroneocystostomies for unilateral reflux had postoperative contralateral reflux (13.33%). Three of these 4 refluxing ureters resolved with medical treatment. A second surgery was needed in only 1 case (3.33%) who did not respond to medical treatment. There was no correlation between the preoperative severity of ipsilateral reflux, intravenous urography findings and the onset of contralateral reflux after unilateral reimplantations. Data from this study and previous works indicated that bilateral reimplantations are not warranted for unilateral refluxing renal units unless there are position and shape anomalies at the ureterovesical angle and a very careful preoperative evaluation of the patients is mandatory in this regard.