Background The Prague C & M criteria, developed for the endoscopic grading of Barrett's esophagus (BE), (C = circumferential length, M=maximal length) were previously validated among a panel of 29 expert endoscopists with a special interest in BE. Its performance among gastroenterology trainees is unknown. Objective To test interobserver agreement among gastroenterology trainees for the Prague C & M criteria, identification of the gastroesophageal junction (GEJ) and the diaphragmatic hiatus. Design A prospective study. Setting Two tertiary referral centers. Patients and Interventions Standardized endoscopic videos were used. Main Outcome Measurements Interobserver agreement. Results Eighteen high-quality videos (normal esophagus, short and long lengths of BE, equally distributed) were independently evaluated by 18 gastroenterology trainees (year 1, n=5; year 2, n=6; year 3, n=7) after administration of a formal teaching module by an expert endoscopist. Overall intraclass correlation coefficients for assessment of the C and M extent of the endoscopic BE segment above the GEJ were 0.94 (95% CI, 0.89-0.98) and 0.96 (95% CI, 0.94-0.98), respectively. The overall intraclass correlation coefficients for GEJ and diaphragmatic hiatus location recognition were 0.92 (0.86-0.96) and 0.90 (0.82-0.95), respectively. The year of training did not affect interobserver agreement. Limitations The use of videos for endoscopic evaluation. Conclusion After standardized teaching, the Prague C & M criteria have high overall validity among gastroenterology trainees irrespective of the level of training for endoscopic evaluation of visualized BE lengths as well as key endoscopic landmarks.