Colorectal cancer is an important global health problem. Randomized trials have shown that screening programs can reduce both colorectal cancer incidence and mortality, and guidelines strongly support screening. Nevertheless, screening rates are relatively low and concerted efforts are being made to increase screening uptake. Many guidelines and practitioners have come to view colonoscopy as the optimal screening strategy. Colonoscopy provides both a gold-standard diagnostic test and, with polypectomy, a therapeutic intervention that can prevent cancer. However, from a public-health perspective, emphasizing colonoscopy is problematic. The efficacy of colonoscopy has not been supported with randomized trial data, accuracy is imperfect, procedural quality is variable, complications are not uncommon, endoscopic capacity is limited, procedure costs are high, and many patients prefer alternative tests. Successful screening programs will need to provide a range of screening modalities and ensure that endoscopic resources are used efficiently.