Upper urinary tract function was evaluated in 15 infants in whom urethral valves were diagnosed. One baby died at 16 days of age and was not completely investigated. In 4, the valves did not have untoward effect on the bladder and the upper urinary tract. In 10 others, function was evaluated using the Hodson index, creatinine, PAH, inuline clearance and renal I123-Hippuran scintigraphy with measurement of the accumulation indices. The various examination procedures were of value in providing precise evaluation of the renal performances at diagnosis as well as in prognosis and follow-up of the function of each kidney.