Advanced biliary tract carcinomas (BTCs) are often diagnosed at an advanced/metastatic stage and have a poor prognosis. The combination of gemcitabine and oxaliplatin (GEMOX) has shown promising activity in this setting. This international phase II study evaluated the efficacy and safety of GEMOX as first-line therapy in patients with advanced BTCs. Eligible patients with previously untreated locally advanced or metastatic BTC received gemcitabine 1000 mg m(-2) (day 1) and oxaliplatin 100 mg m-2 (day 2), every 2 weeks. Seventy patients were enroled; 72.9% had metastatic disease. Sixty-seven patients were treated. There were 10 confirmed partial responses (14.9%; 95% confidence interval (CI), 7.4-25.7%) in the treated population (RECIST). Twenty-four patients (35.8%) had stable disease. The objective response rate was 20.5% in patients with non-gallbladder cancers (9/44 patients) and 4.3% in patients with gallbladder cancers (1/23). Median overall survival for the intent-to-treat population was 8.8 months (95% CI, 6.9-11.1%) and progression-free survival was 3.4 months (95% CI, 2.5-4.6%). Grade 3/4 toxicities included thrombocytopenia (14.9% of patients), alanine aminotransferase elevation (13.4%), anaemia (10.4%), neutropenia (11.9%) and pain (1 1.9%). In this study, GEMOX demonstrated activity in non-gallbladder carcinoma, but poor activity in gallbladder carcinoma. GEMOX is well tolerated in advanced BTCs.