BACKGROUND & AIMS: We evaluated the quality and safety of colonoscopies performed by nurse and physician endoscopy trainees as well as the cost differences. METHODS: We performed a study of 7 nurse and 8 physician (gastroenterology fellows) endoscopy trainees at 2 medical centers in the Netherlands from September 2008 through April 2012. At the beginning of the study, the subjects had no experience in endoscopy; they were trained in gastrointestinal endoscopy according to the regulations of the Dutch Society of Gastroenterology, performing a minimum of 100 colonoscopies. Each trainee then performed 135 consecutive colonoscopies (866 total by nurse trainees and 1080 by physician trainees) under supervision of a gastroenterologist; the colonoscopies were evaluated for quality and safety. We performed statistical analyses of data, assessing multilevel and cost minimization. The mean age of the patients was 57 years, and about half were women in each group. RESULTS: The endoscopic quality and safety were comparable between nurse and physician trainees. Overall rates of cecal intubation were 95% for nurses and 93% for physicians (P = .38), including procedures that required assistance from a supervisor; mean withdrawal times were 10.4 and 9.8 minutes, respectively (P = .44). Each group detected 27% of adenomas and had a 0.5% rate of complication. In both groups, the rates of unassisted cecal intubation gradually increased with the number of colonoscopies performed, from 70% for nurses and 74% for physicians at the beginning to 89% and 86%, respectively, at the end of the assessment period. Using a strategy in which 1 gastroenterologist supervises 3 nurses, the personnel costs decreased from $64.65 to $54.58. CONCLUSIONS: In a supervised setting, nurse endoscopists perform colonoscopies according to quality and safety standards that are comparable with those of physician endoscopist and can substantially reduce costs.