During the last 6 years we managed 20 patients with renal failure owing to bilateral ureteropelvic junction obstruction (12) or ipsilateral ureteropelvic junction obstruction with contralateral renal agenesis, hypoplasia or dysplasia (8). Of the patients 11 underwent emergency dialysis for hyperkalemia, fluid overload or metabolic acidosis. Mean serum creatinine at presentation was 6.5 mg. per cent. Preliminary decompression of the obstructed kidney was done in 14 patients (20 renal units) with a serum creatinine of more than 3 mg. per cent at presentation. Reconstruction was done in all patients (31 of 36 renal units) after decompression and control of infection. Pyeloplasty was done in 24 renal units, vesicopyelostomy in 3 pelvic kidneys and calicoureteroplasty in 2 renal units with an intrarenal pelvis. Two renal units were removed. All patients showed improvement in renal function and the mean postoperative serum creatinine value was 2.05 mg. per cent. The postoperative serum creatinine value showed a significant positive correlation with the initial value as well as with the initial blood urea levels. However, the postoperative serum creatinine value showed no correlation with patient age, duration of symptoms, serum creatinine level after preliminary nephrostomy and presence or absence of urinary infection. Postoperative recovery (on the basis of postoperative serum creatinine levels) in patients who had bilateral ureteropelvic junction obstruction was not different from those with a solitary functioning kidney and ureteropelvic junction obstruction.