In this study, we aimed to detect whether or not visualising ureter and ureteropelvic junction (UPJ) preoperatively is necessary in adult patients who have primer UPJ obstruction. Between January 1995 to June 1999, 46 renal units in 45 patients with primer UPJ obstruction were evaluated. The patients were separated into 2 groups. In group 1, intravenous pyelography (IVP) and renal scintigraphy were performed to 17 renal units preoperatively. In group 2, in addition to these methods, either retrograde pyelography (RGP) or antegrade pyelography (AGP) were performed to 29 renal units. Renal/bladder sonogram was used in patients with poor renal function in IVP or in renal scintigraphy. All the operations were performed through a flank incision. In group 2, additional information was gained for 8 (27.5%) of the renal units preoperatively. No additional information for this group found intraoperatively. In group 1, we found additional information in 4 (23.53%) of the units intraoperatively. All the pathologies in both groups were corrected intraoperatively. Double-J (D-J) stent was used in 6 (35.29%) of the units in group 1 and 8 (27.58%) of the units in group 2 intraoperatively (p > 0.05). In group 2, 4 (13.79%) preoperative complications were seen due to RGP and they were treated either medically or conservatively. In the early postoperative period, a complication observed in 1 (5.88%) of the patients in group 1 and 1 of the patients in group 2 (3.44%) (p > 0.05). The first patient was treated with inserting D-J and the latter one was treated conservatively. In the 3rd postoperative month, success rate was found to be 94.11% in group 1 and 96.55% in group 2 (p > 0.05). Additional pathologies in adult patients with primer UPJ obstruction can be corrected intraoperatively through a flank incision. Therefore, imaging of ureter and UPJ may not be necessary in these patients.