Posterior urethral valves (PUVs) are the commonest cause of severe obstructive uropathy in boys. The incidence of PUV ranges from 1:8000 to 1:25000 boys. Clinical complications result from obstruction, infection or both. Approximately 30% of patients experience end-stage renal failure or chronic renal insufficiency. Over the past decade, the diagnosis of PUV s has been radical1y changed with the development of ultrasound technique. The aim of this study was to determine the frequency of renal damages in children with PUVs. This study was conducted, over two years from March 2001 to February 2003, on twenty boys (median age 26 months, ranged from 1 day up to 10 years) with PUVs were assessed for deterioration of their renal function. The age at presentation in 8 cases was under 1 month, in 5 cases was between 12 months, 4 cases between 1 to 5 years and 3 more than 5 years. The most common clinical feature were fever in 13 cases (65%), dribbling in 9 (45%), dysuria in 7 (35%), abdominal mass in 5 (25%) and hypertension in 4 (20%). Azotemia was detected in 12 cases (60%), abnormal serum creatinine in 11 cases (55%), which in 6 patients was more than 3mg/dl. There were posterior urethral obstruction in all, vesicourethral reflux in 16 (80%) cases and small sized kidneys in 9 (45%) cases. Among these we found one with Bardet-Beidl syndrome and another with Down syndrome. After a supportive and medical treatment, we observed some improvement in serum creatinine levels in all the patients. In addition to the mentioned management 8 cases (including 5 neonates) underwent visicostomy. After initial stabilization, 5 (25%) patients developed chronic renal insufficiency and 4 (20%) progressed to chronic renal failure which is higher than similar cases in the developed countries. In 5 antenatally diagnosed neonates who underwent early vesicostomy, the kidney growth was favorable without subsequentl development of deterioration in their renal function. In conclusion, in order to prevent the serious complications of this obstructive uropathy in these children ultrasounographic screening should be performed prenatally and visicostomy be performed whenever needed.