Acromegaly is associated with an increased risk of colonic polyps. The magnitude of such risk is controversial, and the characteristics that distinguish patients who develop polyps from those who do not are not well established. This study was performed to determine the prevalence of colonic polyps upon the diagnosis of acromegaly and to compare the clinical and biochemical features of patients with and without polyps. Out of 165 patients who underwent a full colonoscopy upon diagnosis of acromegaly, 53 were found to harbor colonic lesions (cases), whereas the remaining 112 were used as controls. Demographic, clinical, and biochemical characteristics were compared between the 2 groups. The prevalence of colonic polyps was 32%, with an estimated relative risk of 6.21 (95% confidence interval [CI] 4.08-9.48). Adenomatous and nonadenomatous polyps were found in 22 and 31 patients, respectively. The most common location was the descending colon. Compared to patients without polyps, subjects with polyps were somewhat older and had significantly higher insulin-like growth factor-1 (IGF-1) levels and a higher prevalence of diabetes. Upon multivariate analysis, only IGF-1 level at diagnosis remained significantly associated with colonic polyps in general and with hyperplastic polyps in particular. Acromegaly is associated with an elevated risk of developing colonic polyps, particularly, distally located hyperplastic lesions. Except for a higher IGF-1 level at diagnosis, no distinctive clinical or biochemical features can be found among those who develop polyps compared to those who do not. CI = confidence interval GH = growth hormone IGF-1 = insulin-like growth factor 1 IQR = inter-quartile range RR = relative risk ULN = upper limit of normal.