Balloon endoscopy has been accepted as an effective tool for examining the small intestine. Two types of balloon endoscopy, single and double, are commercially available. The difference in performance between these 2 types of balloon endoscopy has not yet been elucidated. To compare the yield of single-balloon endoscopy (SBE) and double-balloon endoscopy (DBE). Single-center, randomized, controlled trial. University hospital in Tokyo, Japan. Patients with suspected small-bowel disease. SBE and DBE. Outcomes were the total enteroscopy rate, diagnostic yield, complication rate, and clinical outcomes. Analysis was done by intent to treat. The study started in April 2008 and was terminated in April 2010 because of an obvious disadvantage for the SBE group. Thirty-eight patients were enrolled in the study; 18 patients were assigned to the SBE group and 20 to the DBE group. The total enteroscopy rate was 0% in the SBE group and 57.1% in the DBE group (P = .002). In terms of complications, the DBE group had 1 patient with Mallory-Weiss syndrome, and the SBE group had 1 patient with hyperamylasemia. There was no difference in the overall diagnosis rate between the SBE and DBE groups (61.1% vs 50.0%, P = .49). There was no difference in therapeutic outcome between the SBE and DBE groups (27.8% vs 35.0%, P = .63). Relatively small number of study patients. Total enteroscopy is more easily performed with DBE than with SBE. Copyright © 2011 American Society for Gastrointestinal Endoscopy. Published by Mosby, Inc. All rights reserved.