Twenty-five resident physicians performed 495 fiberoptic sigmoidoscopic examinations that were graded for overall skill according to a six-point competence scale. In general, 24 to 30 examinations were required to become competent at fiberoptic sigmoidoscopy. Trainees with prior rigid sigmoidoscopy experience achieved competence more quickly than those with no prior rigid sigmoidoscopy experience. As experience increased, unassisted insertion distance and luminal visualization increased, insertion time and assisted time decreased, and management scores and percent correct diagnoses improved. Trainees detected 93 to 100 percent of polyps and cancers viewed by the experienced sigmoidoscopist once competence was achieved. These data indicate that programs for training primary care physicians in fiberoptic sigmoidoscopy are feasible, help define the number of examinations required to become competent, and indicate that such trainees should be effective in cancer screening.