To assess the effectiveness of a training program in flexible sigmoidoscopy for family practice residents, we prospectively studied the performance of four residents during their training and after graduation. One hundred and four training exams performed with the assistance of an experienced gastroenterologist were compared with 118 unassisted post-training, post-residency exams. The mean depth of insertion for the post-training period was 51.1 +/- 1.2 cm, which was significantly greater (P less than .05, Student's t test) than the mean training period depth of 47.6 +/- 1.2 cm. There was no significant difference in the identification of polyps or cancer between the training and post-training periods. The mean duration of an exam was 17.3 +/- 0.6 minutes in the post-training period. No significant complications were encountered in either period. The residency trained family physicians obtained results similar to those reported by trained endoscopists in depth of examination and pathology detected, although their examinations required more time. We conclude that this model of training was effective in the development of flexible sigmoidoscopy procedural skill for family practice residents.