Background: Although colonoscopy is the criterion standard for detecting colorectal adenomas and cancers, a significant percentage of adenomas are missed. Objective: To compare forward-viewing with ultrawide-viewing colonoscopy in the detection of simulated colon polyps in an in vitro colon model. Design: Prospective, multicenter. Setting: Six endoscopy units (3 in the United States and 3 in Israel). Patients: In vitro colon model with simulated colon polyps (n = 21 metallic beads). Interventions: Detection of simulated colon polyps on colonoscope withdrawal. Main Outcome Measurements: Incremental detection of simulated colon polyps and endoscopist evaluation of the usability, visibility, and maneuverability of ultrawide-viewing colonoscopy. Results: On forward-viewing colonoscopy, the number of simulated polyps (mean ± standard deviation) detected per endoscopist was 11.1 ± 2.3 polyps, a 52.9% detection rate. Simulated polyp detection rates per colon segment were 3.0 ± 0.93 (60.0%) right colon, 2.4 ± 0.87 (48.0%) transverse colon, and 5.7 ± 1.5 (51.8%) left colon. On ultrawide-viewing colonoscopy, the simulated polyp detection rate per endoscopist significantly increased to 18.0 ± 1.98 polyps, an overall 85.7% polyp detection rate (P <.001). Simulated polyp detection rates were also significantly higher by using the ultrawide-viewing mode in each colon segment, 4.5 ± 0.65 polyps (90.0%) right colon, 4.0 ± 0.87 (80.0%) polyps transverse colon, and 9.6 ± 1.28 polyps (87.3%) left colon (all comparisons, P <.001). Importantly, the ultrawide-viewing mode detected significantly more "hidden" simulated polyps (81.9% vs 31.9%, P <.0001). Limitations: Nonrandomized design, use of a colon model, and "simulated" colon polyps. Conclusions: Ultrawide-view colonoscopy significantly improved simulated polyp detection in a colon model. Clinical studies in human subjects should be pursued to further evaluate this new endoscopic technology.