Abstract Polymorphisms of the transcription factor 7–like 2 (TCF7L2) gene have been associated with insulin sensitivity and diabetes, and the TCF7L2 gene is involved in the Wnt/β-catenin signaling pathway, all factors thought to be important in the etiology of colon cancer. In this confirmatory study, we evaluated the rs7903146 TCF7L2 polymorphism with colon cancer using previously collected data on 1,578 cases and 1,966 controls. We did not observe a statistically significant association between the rs7903146 polymorphisms and risk of colon cancer [odds ratio (OR), 1.12; 95% confidence interval (95% CI), 0.98-1.28] when evaluating the total population. We did, however, observe a statistically significant interaction between the rs7903146 TCF7L2 polymorphism and recent use of aspirin/nonsteroidal anti-inflammatory drugs (NSAID; P = 0.001). Increased colon cancer risk associated with the T allele was restricted to those without recent use of aspirin/NSAIDs (OR, 1.65; 95% CI, 1.35-2.02, relative to recent aspirin users, i.e., use of aspirin/NSAIDS within the 2 years before diagnosis, with the CC genotype). Among individuals who reported recent use of aspirin/NSAIDs, the T allele reduced risk of colon cancer (OR, 0.78; 95% CI, 0.62-0.98) in a dose-response fashion (P for linear trend across genotypes = 0.03). These data suggest that colon cancer risk associated with the rs7903146 TCF7L2 polymorphism is modified by use of aspirin/NSAIDs. (Cancer Epidemiol Biomarkers Prev 2008;17(4):978–82)