OBJECTIVE: The cost-effectiveness of oxaliplatin in combination with 5-fluorouracil/leucovorin (5FU/LV)-the FOLFOX regimen-was compared with that of 5FU/LV alone as adjuvant therapy for patients with stage III colon cancer, from the perspective of the Cancer Care Ontario New Drug Funding Program. In the mosaic (Multicenter International Study of Oxaliplatin/5-Fluorouracil/Leucovorin in the Adjuvant Treatment of Colon Cancer) trial, the FOLFOX regimen significantly improved disease-free survival. The mosaic trial formed the basis of the present analysis. METHODOLOGY: Extrapolated patient-level data from the mosaic trial were used to model patient outcomes from treatment until death. Utilities were obtained from the literature. Resource utilization data were derived from the mosaic trial and supplemented with data from the literature. Unit costs were obtained from the Ontario Ministry of Health and Long-Term Care, the London Health Sciences Centre, and the literature. RESULTS: Lifetime incremental cost-effectiveness ratios for FOLFOX compared with 5fu/lv were CA$14,266 per disease-free year, CA$23,598 per life-year saved, and CA$24,104 per quality adjusted life-year (QALY) gained, discounting costs and outcomes at 5% per annum. These results were stable for a wide range of inputs; only utility values associated with relapse seemed to influence the cost-effectiveness ratios observed. CONCLUSIONS: With an incremental cost of CA$24,104 per QALY gained, FOLFOX is a cost-effective adjuvant treatment for stage iii colon cancer. Compared with 5fu/lv alone, this regimen offers better clinical outcomes and provides good value for money.