According to the IDEA trial, 6-month adjuvant chemotherapy should remain the treatment standard in stage III T4 or N2 colon cancer. The relatively poor survival in this high-risk subgroup—a 3-year disease-free survival (DFS) rate of 65%—and the potential synergistic efficacy of 5-fluorouracil (5-FU), oxaliplatin, and irinotecan suggest that FOLFIRINOX may be a regimen of particular interest in this setting. This multicenter international phase 3 trial (ClinicalTrials.gov NCT02967289) being conducted in 49 centers in France and Canada plans to randomize (1:1; minimization method) 640 patients aged 18 to 70 years with Eastern Cooperative Oncology Group performance status ≤ 1. Randomization occurs within 42 days (with treatment initiated within 56 days) after curative-intent R0 surgical resection of a pT4N1 or pT1-4N2 colon adenocarcinoma. Patients will be randomized to receive adjuvant modified FOLFIRINOX (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, irinotecan 180 mg/m2, and 5-FU 2.4 g/m2 over 46 hours) or modified FOLFOX6 (oxaliplatin 85 mg/m2, leucovorin 400 mg/m2, 5-FU bolus 400 mg/m2, then 2.4 g/m2 over 46 hours) every 2 weeks for 24 weeks (12 cycles). Patients will be followed for 5 years after the end of adjuvant chemotherapy. A gain of 9% in 3-year DFS (primary end point) is expected (74% in the experimental arm vs. 65% in the control arm; α, 5% 2-sided log-rank test; 1-β, 80%). Secondary end points of this study include 2-year DFS, overall survival, and toxicity.