OBJECTIVES: FOLFOX (folic acid [l-LV], 5-FU and oxaliplatin) is a standard therapy for metastatic colorectal cancer. FOLFOX in adjuvant therapy was approved in 2009. However cost-effectiveness of FOLFOX, which can prolong DFS (disease free survival) is not known. METHODS: We performed cost-effectiveness analysis of FOLFOX in adjuvant therapy for stage3 colon cancer compared with FU/LV as a standard regimen. Our analysis is based on the patient-level data of MOSAIC (the Multicenter International Study of Oxaliplatin/5-Fluorouracil/Leucovorin in the Adjuvant Treatment of Colon Cancer) trial. Survival curve of DFS and OS (overall survival) was extrapolated by cure model, which uses parametric regression considering some patients can cure without recurrence. Death of any other causes was treated as competing risk. Expected value of mean survival year was gained by calculating area under the estimated survival curve during 15 years. QALY (quality adjusted life year) was calculated weighting survival time by utility scores. Since our analysis is from the perspective of healthcare payer, only direct medical costs were included. Three percent annual discount rate was used for both costs and outcome. RESULTS: Adjuvant FOLFOX therapy for stage 3 colon cancer patients can gain more QALY than standard FU/LV therapy. The difference of both therapy is about 0.5 QALY. ICER (incremental cost-effectiveness ratio) of FOLFOX compared with FU/LV estimated to be less than JPY 2.5 million (US$28,000, US$ 1=JPY 90) per QALY. This value is thought to be a little conservative because time horizon of our analysis is 15 years, not life time to avoid uncertainty of long term future. CONCLUSIONS: FOLFOX therapy in adjuvant of stage3 colon cancer is  cost-effective. The ICER compared with FU/LV is acceptable from the Japanese healthcare payer.