OBJECTIVES: Cetuximab, a chimeric monoclonal antibody, improved the overall survival and progression free survival of chemorefractory metastatic colorectal cancer (mCRC) KRAS wild (unmutated) type patients in the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) CO.17 study. The objective of our study was to conduct the cost-effectiveness analysis of cetuximab plus best supportive care versus best supportive care alone in KRAS wild type mCRC patients. METHODS: A Markov cohort simulation model was used to simulate therapy costs and effectiveness from the US societal perspective.  All estimates of costs and effectiveness were obtained from the literature.  The cost-effectiveness ratio was reported as incremental cost per quality-adjusted life-year (QALY) gained.  A life time horizon was used.  Base case costs and QALYs were discounted at an annual rate of 3%.  All costs were adjusted to 2011 US dollars.  One-way and probabilistic sensitivity analyses were used to determine the robustness of the model’s results using @Risk.  The model was developed using Microsoft Excel.  RESULTS: The incremental cost with cetuximab compared with best supportive care alone was $93,934 and the mean gains in quality adjusted survival were 0.30 QALYS. This resulted in base case ICER of $313,113 per QALY gained. The results were highly sensitive to the cost of cetuximab and health state utility values.  CONCLUSIONS: The incremental cost effectiveness ratio of $313,113 per QALY gained for cetuximab plus BSC compared with BSC alone suggests that cetuximab is not cost effective in KRAS wild type patients with metastatic colorectal cancer even with a willingness-to-pay cut-off threshold of $120-$150,000 per QALY gained.