The use of carcinoembryonic antigen (CEA) to monitor patients after intentionally curative colon cancer resection can have advantages (improved life expectancy as a result of early detection of recurrences) as well as disadvantages (false-positive CEA rises and early detection of incurable recurrences in asymptomatic patients). This study estimated how the favorable and unfavorable effects of CEA monitoring affect life expectancy and quality of life of colon cancer patients. These effects were simulated using a Markov analysis for which the variables had been defined on the basis of data found in literature. The influence of CEA monitoring on quality adjusted life expectancy appears to be modest and varies, according to the data used, from an average increase of +7 days (+0.3%) to an average decrease of -5 days (-0.09%). This value is dependent, among other things, on patient related variables; the adverse effects especially dominate in older patients with a favorable Dukes' stage of the primary tumor and if operative mortality exceeds 2%. The total cost of CEA monitoring, including diagnosis and therapy performed as a result of true- or false-positive CEA rise, is considerable. High cost and low return leads to a high marginal cost-effectiveness ratio, which varies from $22,963 to $4,888,208 per quality adjusted life year saved. It is concluded that CEA monitoring should not be used for routine following of colon cancer patients, as its advantages have so far been demonstrated insufficiently.