Examination of the entire sigmoid was not achieved in approximately one-quarter of patients undergoing screening flexible sigmoidoscopy, mainly because of discomfort. The descending colon is intubated in a minority of cases (using standard instruments), even after 60 cm has been inserted. Alternative instruments with different shaft characteristics (floppy, narrow calibre, 80-100 cm in length) may be necessary to ensure deeper routine intubation in nonsedated patients.