PURPOSE No standard adjuvant treatment currently is recommended in localized biliary tract cancer (BTC) after surgical resection. We aimed to assess whether gemcitabine and oxaliplatin chemotherapy (GEMOX) would increase relapse-free survival (RFS) while maintaining health-related quality of life (HRQOL) in patients who undergo resection. PATIENTS AND METHODS We performed a multicenter, open-label, randomized phase III trial in 33 centers. Patients were randomly assigned (1:1) within 3 months after R0 or R1 resection of a localized BTC to receive either GEMOX (gemcitabine 1,000 mg/m² on day 1 and oxaliplatin 85 mg/m² infused on day 2 of a 2-week cycle) for 12 cycles (experimental arm A) or surveillance (standard arm B). Primary end points were RFS and HRQOL. RESULTS Between July 2009 and February 2014, 196 patients were included. Baseline characteristics were balanced between the two arms. After a median follow-up of 46.5 months (95% CI, 42.6 to 49.3 months), 126 RFS events and 82 deaths were recorded. There was no significant difference in RFS between the two arms (median, 30.4 months in arm A v 18.5 months in arm B; hazard ratio [HR], 0.88; 95% CI, 0.62 to 1.25; P = .48). There was no difference in time to definitive deterioration of global HRQOL (median, 31.8 months in arm A v 32.1 months in arm B; HR, 1.28; 95% CI, 0.73 to 2.26; log-rank P = .39). Overall survival was not different (median, 75.8 months in arm A v 50.8 months in arm B; HR, 1.08; 95% CI, 0.70 to 1.66; log-rank P = .74). Maximal adverse events were grade 3 in 62% (arm A) versus 18% (arm B) and grade 4 in 11% versus 3% ( P < .001). CONCLUSION There was no benefit of adjuvant GEMOX in resected BTC despite adequate tolerance and delivery of the regimen.