Background: Observation alone after initial treatment of unresectable metastatic colorectal cancer is often anxiety provoking for physician and patient alike. The CAIRO 3 trial suggested the efficacy of maintenance capecitabine and bevacizumab in improving overall survival for such patients. We hypothesized that the cost effectiveness for maintenance capecitabine and bevacizumab would be worse than accepted population thresholds. Methods: Data from the CAIRO-3 trial was used to populate a semi-markov model, in which patients transitioned between different disease and complication based states. Transition probabilities were extratcted from the trial. Costs were determined from a thirs payer persective from the Medicare part B ASP drug pricing file. Utility was converted from the global quality of life scale. Incremental cost effectiveness ratios were calculated. Results: Cost of the maintenance arm after 10 cycles was $108,848 with a gain in 14.93 quality adjusted life months, while the quality adjusted life months gained at no cost in the observation arm was 13.67. This yielded an ICER of $1,036,648/QALY. Two way sensitivity analyses demonstrated dominance of observation across a wide range of parameters unless the cost per cycle was < $6250. Conclusions: Maintenance capecitabine and bevacizumab is not cost effective and is higher than the willingness to pay threshold for any developed nation. Reducing drug pricing is the only way to financially support the argument for this treatment strategy.