Ureteropelvic junction obstruction (UPJ) in adults is more common than generally appreciated. It may mimic other diseases and may be associated with abdominal pain, hypertension, and recurrent pyelonephritis. Diagnosis and surgical correction were frequently delayed with an average duration of symptoms of 3.2 years for 31 adult patients. Only 4 adults (13%) were diagnosed at the time of their initial onset of symptoms. Nephrectomies were performed on 24 per cent of renal units. Accessory lower pole renal vessels were found in 52 per cent of the adults with UPJ obstruction, twice the rate found in children. Intravenous digital subtraction angiography and diuretic radionucleotide renography should be considered in the evaluation of an adult patient with a UPJ obstruction because of the high rate of accessory vessels. If accessory vessels are present on the contralateral side, especially postnephrectomy, there is heightened concern for the remaining kidney and close follow-up with ultrasonography is recommended.