Two groups of patients, with laparoscopic cholecystectomy (LC) were prospectively studied. All patients had serial plain abdominal X-ray examinations at various intervals after operation, to record the position of clips placed during LC. Seventy-one patients had less cystic duct (CD) dissection and > or =4 clips placed during the procedure. One hundred and fifteen patients had a larger CD dissection and only 4 clips placed (2 on the cystic artery and 2 on the CD, without additional clips on smaller vessels). In the former group, 7 patients had clip migration within 1 month and 11 within 1 year vs 1 either at 1 month or 1 year in the latter group (p = 0.01 and <0.001, respectively). During the follow-up, a 72-year-old man belonging to the former group had a recurrent common duct brown pigment stone containing a metallic clip 26 months after operation. He was treated successfully by endoscopic sphincterotomy. Factors predisposing to clip migration were short cystic stump, inadvertent clip dislodgment or incorrect placement, cystic duct ischemic necrosis, and local suppurative complications. Data from 29 patients with GS formed around suture material or phytobezoars observed during a prospective study and from the physicochemical and structural analysis of a cumulative series of 64 GS containing foreign bodies are also presented and discussed. It is suggested that metallic clips can migrate from their initial sites at various intervals within the peritoneal cavity or into the common duct and serve as a nidus for GS formation. Metallic clip migration in most cases is due to technical factors and can usually be prevented. However, it is not possible to prevent either clip migration or GS formation in every case, since even well-placed clips can migrate due to suppurative complications or local ischemic damage, and, once that penetration within the bile tract has occurred, GS are usually going to form, irrespective of the nature and the shape of the foreign body.