['Guidelines recommend that patients with colon adenomas undergo periodic surveillance colonoscopy. The purpose of this study was to estimate the cost-effectiveness of these recommendations.', 'We developed a Markov model to study various surveillance strategies from the perspective of a long-term payer. We modeled a cohort of 50-year-old patients with newly diagnosed adenomas, following them until death. Thirty percent of the population was assumed to be at high risk for colorectal cancer. Costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) were measured.', 'Performing colonoscopies every 3 years in high-risk patients and every 10 years in low-risk patients (3/10 strategy) was more costly but also more effective than no surveillance, with an ICER of $5,743 per QALY gained. Compared with this 3/10 strategy, a 3/5 strategy was considerably more costly but only marginally more effective, with an ICER of $296,266 per QALY. A 3/3 strategy was more costly and less effective than a 3/5 strategy (dominated). Results were most sensitive to the annual probability of advanced adenoma formation and the relative risk (RR) of advanced adenoma formation in high-risk versus low-risk patients. Assuming that the probability of advanced adenoma formation was 1.3% per year (base: 0.5%), the ICER of the 3/5 strategy was <$50,000 per QALY gained if the RR of advanced adenoma formation was <2.4 (base: 3.9).'] Is surveillance colonoscopy cost-effective for patients with adenomas who are at high risk of colorectal cancer?