Of all patients operated for colorectal cancer, 1 in 3 will suffer from cancer recurrence, and most of these patients will die from disseminated disease. Postoperative follow-up aims at improving these grim figures. This sound idea has not been supported by any empirical data. In the current article, we discuss some theoretical issues concerning colorectal cancer follow-up, and present results of a cost-effectiveness analysis, used to model the natural history of colorectal cancer recurrence and the costs and effects of follow-up and re-operation. The expected results of three policies were calculated: no follow-up, selective follow-up and intensive follow-up. For most patients, follow-up will only lead to a significant increase in costs, without increase in (quality-adjusted) life expectancy. Colorectal cancer follow-up is not evidence-based medicine .