BACKGROUND The clinical outcome of ureteral obstruction secondary to gastric cancer remains unclear. The present study was designed to evaluate the clinical outcome and predictive factors of survival in patients with ureteral obstruction secondary to gastric cancer. METHODS Twenty-five consecutive patients with ureteral obstruction secondary to gastric cancer between January 1998 and December 2007 were retrospectively analyzed. All patients had hydronephrosis; 13 patients had bilateral hydronephrosis, and 12 patients had unilateral hydronephrosis. RESULTS Ten patients presented with pain, 3 patients with urinary tract infection, and 2 patients with acute renal failure. Seven (58%) of 12 patients with unilateral ureteral obstruction experienced progression to bilateral ureteral obstruction during the follow-up period. Eighteen patients (61%) were eventually managed with urinary diversion. In total, 5 patients were managed with percutaneous nephrostomy, and 15 patients with retrograde ureteral stenting. All symptomatic patients responded to urinary diversion. The overall median survival was 5.8 months, and the 6-month and 1-year survival rates were 48 and 32%, respectively. Chemotherapy was found to be the only independent predictor of survival (p=0.0498). Median survival in patients who received chemotherapy was 11.2 months, in comparison to 3.1 months in patients who did not receive chemotherapy (p=0.0002). CONCLUSIONS The prognosis of ureteral obstruction secondary to gastric cancer was extremely poor, particularly when chemotherapy was not administered. The indications for palliative urinary diversion should be determined after considering the patient's symptoms, the expected survival time, the possibility of further chemotherapeutic options, and the current quality of life.