Sigmoidoscopy could aid in the control of large bowel cancer by early detection of the 55% of colorectal cancers that develop in the rectosigmoid and by the identification and eradication of significant rectosigmoid adenomas. Rigid sigmoidoscopy has had poor patient acceptance and therefore has not been successful. The present study is a prospective randomized trial to evaluate patient response to flexible as compared with rigid sigmoidoscopy. Patients reported significantly less discomfort (10.1% versus 29.7%), anxiety (9.8% versus 27.6%) and embarrassment (5.2% versus 12.8%) during flexible as compared with rigid sigmoidoscopy. Flexible sigmoidoscopy appears to have better patient acceptance than rigid sigmoidoscopy (P less than 0.01). This could enhance its value as a cancer-control instrument. This article addresses the feasibility of sigmoidoscopy. Its validity also needs to be addressed within the framework of a long-term trial, evaluating mortality for rectosigmoid cancer.