OBJECTIVES: To predict the expected incremental costs and mean life-years associated with adding bevacizumab to FOLFOX4 in the adjuvant treatment of patients with AJCC/UICC stage III colon carcinoma following surgical resection. METHODS: A three-health state (disease-free survival [DFS], relapse/new occurrence of colon carcinoma, and death) Markov model was used to explore the effects of adding one year of adjuvant treatment with bevacizumab to the existing adjuvant FOLFOX4 treatment regimen. Baseline DFS for FOLFOX4-treated patients was based on published data from the MOSAIC trial (André et al 2004). The relative risk reduction for bevacizumab was based on protocol assumptions for the ongoing phase III AVANT study. Outcomes included life-years, QALYs, direct costs, and incremental cost-effectiveness ratios (ICERs) expressed as costs per QALY or life-year gained. A life time horizon (40 years) was used; after 8 years, patients were assumed to only be at risk for death. Costs and outcomes were discounted at 3.5% per annum. Sensitivity analyses were performed to identify influential parameters in the model. RESULTS: Undiscounted mean life expectancy for patients treated with FOLFOX4 was estimated at 15.9 years. Assuming the addition of bevacizumab reduces the risk of relapse by 23% in the first 3 years after surgery, as described in the protocol, and by 10% in the following 5 years, mean survival was estimated to increase to 18.1 years (10.8 to 12.1 years when discounted). The discounted ICER was £19,939/life year gained. Sensitivity analysis showed that assumptions relating to the magnitude of the relapse risk reduction and the duration of risk reduction were the most critical determinants of the ICER.  CONCLUSIONS: Addition of bevacizumab to FOLFOX4, the current standard regimen for patients with stage III colon carcinoma, is expected to improve clinical outcomes and to be a cost-effective treatment option from a UK perspective.