&NA;Eighteen trainees with no prior fiberoptic endoscopic experience performed a total of 305 fiberoptic sigmoidoscopies using a colonoscope. Basic training, consisting of reading materials, lecture instructions, practice on a colon model, and observation of procedures, was completed prior to beginning patient examinations. Additional instruction was given between examinations. The performance of these examinations was an individual effort on the part of the trainee without verbal or mechanical assistance from the instructor after the initial ten examinations. All were performed with an instructor viewing through a teaching attachment. Total insertion distance was ≥30,≥40,≥50, ≥60 cm in 65, 60, 46, and 20 percent of examinations, respectively. Overall performance was better in those with prior rigid sigmoidoscopic experience (20 examinations). The mean examination time was 11.8 minutes. These data help to define the appropriate length of fiberoptic sigmoidoscope recommended for use by inexperienced endoscopists.