Background. Balloon-assisted enteroscopy has been recognized as a useful method for performing endoscopic retrograde cholangiopancreatography in patients with complex postsurgical anatomy. Objective. To clarify the usefulness of single-balloon enteroscopy for performing endoscopic retrograde cholangiopancreatography successfully in patients after Billroth II gastrectomy or Roux-en-Y reconstruction and compare it with that of conventional endoscopy. Patients and Methods. We analyzed 204 endoscopic retrograde cholangiopancreatography procedures performed at Kyoto Second Red Cross Hospital between 1997 and 2011 in 93 patients after Billroth II gastrectomy and Roux-en-Y reconstruction with gastrectomy and choledochojejunostomy. We compared recent results with those achieved before the advent of single-balloon enteroscopy ("pre-single-balloon enteroscopy" group versus "post-single-balloon enteroscopy" group). Results. The rate of reaching the blind end was 11/12 (91.7%) in post-single-balloon enteroscopy Roux-en-Y gastrectomy cases and 3/9 (33.3%) in pre-single-balloon enteroscopy Roux-en-Y gastrectomy cases (P = 0.015). The rate of accomplishing target procedures was 7/12 (58.3%) in post-single-balloon enteroscopy Roux-en-Y gastrectomy cases. No significant difference was found in the rates for Billroth II gastrectomy cases. Conclusion. The single-balloon enteroscopy system is effective in reaching the blind end in patients who have undergone Roux-en-Y reconstruction; however, further innovations are needed to accomplish endoscopic retrograde cholangiopancreatography-related procedures.