AIM: To identify whether the forceps estimation is more useful than visual estimation in the measurement of colon polyp size.METHODS: We recorded colonoscopy video clips that included scenes visualizing the polyp and scenes using open biopsy forceps in association with the polyp, which were used for an exam. A total of 40 endoscopists from the Busan Ulsan Gyeongnam Intestinal Study Group Society(BIGS) participated in this study. Participants watched 40 pairs of video clips of the scenes for visual estimation and forceps estimation, and wrote down the estimated polyp size on the exam paper. When analyzing the results of the exam, we assessed interobserver differences, diagnostic accuracy, and error range in the measurement of the polyp size.R E S U LT S : The overall intra-class correlation coefficients(ICC) of inter-observer agreement for forceps estimation and visual estimation were 0.804(95%CI: 0.731-0.873, P < 0.001) and 0.743(95%CI: 0.656-0.828, P < 0.001), respectively. The ICCs of each group for forceps estimation were higher than those for visual estimation(Beginner group, 0.761 vs 0.693; Expert group, 0.887 vs 0.840, respectively). The overall diagnostic accuracy for visual estimation was 0.639 and for forceps estimation was 0.754(P < 0.001). In the beginner group and the expert group, the diagnostic accuracy for the forceps estimation was significantly higher than that of the visual estimation(Beginner group, 0.734 vs 0.613, P < 0.001; Expert group, 0.784 vs 0.680, P < 0.001, respectively). The overall error range for visual estimation and forceps estimation were 1.48 ± 1.18 and 1.20 ± 1.10, respectively(P < 0.001). The error ranges of each group for forceps estimation were significantly smaller than those for visual estimation(Beginner group, 1.38 ± 1.08 vs 1.68 ± 1.30, P < 0.001; Expert group, 1.12 ± 1.11 vs 1.42 ± 1.11, P < 0.001, respectively).CONCLUSION: Application of the open biopsy forceps method when measuring colon polyp size could help reduce inter-observer differences and error rates. AIM: To identify whether the forceps estimation is more useful than visual estimation in the measurement of colon polyp size. METHODS: We recorded colonoscopy video clips that included scenes visualizing the polyp and scenes using open biopsy forceps in association with the polyp, which were used for an exam. A total of 40 endoscopists from the Busan Ulsan Gyeongnam Intestinal Study Group Society (BIGS) participated in this study. Participants watched 40 pairs of video clips of the scenes for visual estimation and forceps estimation, and wrote down the estimated polyp size on the exam of the exams, we assessed interobserver differences, diagnostic accuracy, and error range in the measurement of the polyp size. RESU LT S: The overall intra-class correlation coefficients (ICC) of inter-observer agreement for forceps estimation and visual estimation were 0.804 (95% CI: 0.731-0.873, P <0.001) and 0.743 (95% CI: 0.656-0.828, The overall diagnostic accuracy for visual estimation was 0.639 and for forceps estimation was 0.754 (P <0.001 for each group for forceps estimation were higher than those for visual estimation (Beginner group, 0.761 vs 0.693; Expert group, 0.887 vs 0.840, respectively) In the beginner group and the expert group, the diagnostic accuracy for the forceps estimation was significantly higher than that of the visual estimation (Beginner group, 0.734 vs 0.613, P <0.001; Expert group, 0.784 vs 0.680, P <0.001, The overall error range for visual estimation and forceps estimation were 1.48 ± 1.18 and 1.20 ± 1.10, respectively (P <0.001). The error ranges of each group for forceps estimation were significantly smaller than those for visual estimation (Beginner group, 1.38 ± 1.08 vs 1.68 ± 1.30, P <0.001; Expert group, 1.12 ± 1.11 vs 1.42 ± 1.11, P <0.001, respectively) .CONCLUSION: Application of the open biopsy forceps method when measuring colon polyp size could help redu ce inter-observer differences and error rates.