Wireless capsule endoscopy is a simple, non-invasive technique for the visualization of the entire small bowel. It was introduced in clinical praxis in 2001 and has already become the method of choice for the investigation of small-bowel pathology. Capsule retention is a major complication, with an overall incidence of 1-2%, although reported rates vary widely from 0% to 21%, depending on the indication for the examination. This complication can occur at any level of the gastrointestinal tract and in most cases runs asymptomatically. However, symptomatic bowel obstruction requiring surgical or endoscopic removal of the impacted capsule can occur. Rarely, capsule retention can lead to intestinal perforation. Despite several years of experience with wireless capsule endoscopy, there is up to the present no safe means of predicting capsule retention. Radiological studies have a low diagnostic yield and tend to underestimate or overestimate small-bowel strictures. The role of the new generation patency capsule (Agile patency capsule) needs to be further documented. The experts agree that obtaining a careful history is perhaps the best single method to detect the possibility of retention.