We have treated seven children with multicystic dysplastic kidney during the last 15 years. Three of then presented contralateral upper urinary tract anomalies. Four cases were diagnosed during prenatal period and three during the first term of life. We did analytic kidney function evaluation, ultrasound examination, voiding cystourethrography, radionuclide scan, gammagraphy, excretory urography and urinary cultures in all cases. We have found a vesicoureteral reflux with a bifid pelvis associated in the same child and two other cases with nonobstructive hydronephrosis. The child with vesicoureteral reflux presented also ipsilateral anomalies like a bladder diverticulum and an incomplete urethral duplication. One child with hydronephrosis opposite to the multicystic dysplastic kidney, also presented a bowel malrotation and a congenital cardiopathy, as extra-urologic associated anomalies.