BACKGROUND FOLFOX2, a bimonthly regimen of high-dose leucovorin (LV), 48-hour continuous infusion of 5-fluorouracil (5-FU) (LV-5-FU) and oxaliplatin (100 mg/m2) produced a high response rate (46%; 95% confidence interval (95% CI): 31%-60%) in 5-FU pre-treated patients with metastatic colorectal cancer. In this phase II study, pre-treated patients were given a lower dose of oxaliplatin to reduce the toxic effects of the regimen. METHODS Thirty patients with advanced colorectal adenocarcinoma and progression while receiving bimonthly LV-5-FU (LV: 500 mg/m2, 5-FU: 1.5-2 g/m2/22 hours, days 1-2, every two weeks), were given the same LV-5-FU schedule with the addition of oxaliplatin (85 mg/m2) every two weeks (FOLFOX3). RESULTS The main toxic effects were peripheral neuropathy (90%) with four severe sensitive neuropathies (WHO grade 2: 13%). The response rate was 20% (95% CI: 8%-39%). Median progression-free survival was 26 weeks, median survival was 57 weeks from the start of FOLFOX3 and median duration of the response was 37 weeks. CONCLUSIONS Results obtained with FOLFOX3 confirmed the synergy between oxaliplatin and 5-FU in 5-FU-resistant metastatic colorectal cancer. However, the response rate seems to be lower than that obtained with FOLFOX2. Further studies to determine the best oxaliplatin dose intensity are in progress.