Double-balloon endoscopy (DBE) was developed based on the principle of preventing stretching of the intestinal tract by anchoring the convoluted intestinal tract with an endoscope and overtube fitted with inflatable balloons. The DBE system includes the main body of the endoscope with a built-in air channel, a balloon attached to the tip of the endoscope, an overtube with a hydrophilic coating equipped with an inflatable balloon, and a balloon controller that safely inflates/deflates the two balloons. At present, there are three different types of endoscopes for DBE. The indications for DBE include the diagnosis or treatment of various small intestinal conditions such as obscure gastrointestinal bleeding, Crohn’s disease, and benign and malignant tumors. In addition, DBE can be used to approach the surgically modified intestinal tract; conventional endoscopes have difficulty in that situation. DBE can be used for colonoscopy in cases in which it is difficult to insert a conventional colonoscope. In the future, DBE will have the potential for wider use in routine colonoscopy because the insertion technique is easy and reliable.