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In 1992, a case-control study of sigmoidoscopy provided the first convincing evidence that colorectal cancer screening is effective. Since then, other case-control studies of flexible sigmoidoscopy have shown reductions in incidence of and mortality from distal colon cancer, and case-control studies of colonoscopy have shown risk reductions, especially from distal colon cancer. The randomized NORCCAP trial of sigmoidoscopy screening provided strong evidence of reductions in cancer mortality among attendees to sigmoidoscopy screening, but long-term follow-up results are pending. Now, the most convincing evidence to date from a randomized study with 11 years of follow-up shows that flexible sigmoidoscopy screening reduces incidence of and mor…