OBJECTIVE To determine the efficacy of peroral electrohydraulic lithotripsy performed with an extra large duodenoscope (outside diameter 14.8 mm) and a choledochoscope with a diameter of 4.1 mm (Olympus "mother and baby" endoscope system) in the removal of very large stones from the common bile duct. METHODS Prospective study of patients with giant stones in the common bile duct that were resistant to extraction by conventional means. METHODS Endoscopy unit at a university hospital. METHODS Four women and one man aged 48-82 (mean 66.4 years) with a total of nine stones in their common bile ducts ranging from 2.2 to 3.6 cm in diameter. METHODS Peroral electrohydraulic lithotripsy was performed after intravenous sedation and under antibiotic cover. Two endoscopists took part in each procedure, coordination being achieved by means of a video monitor. The procedures were performed with a Lithotron EL-23 lithotripter and a 3 French lithotripsy probe inserted through the choledochoscope under direct vision. METHODS Complete clearance of the common bile duct confirmed by occlusion cholangiography. RESULTS All nine stones (mean minimal diameter 2.6 cm; mean maximal diameter 3.1 cm) were successfully fragmented by electrohydraulic lithotripsy, allowing subsequent extraction with the aid of endoscopy and clearance of the common bile duct. A median of three (range two to five) sessions of endoscopic retrograde cholangiopancreatography were required to achieve complete clearance of the ducts. Patients stayed a median of eight days in hospital after lithotripsy (range eight to 14). There were no complications. CONCLUSIONS Peroral electrohydraulic lithotripsy offers a safe and effective alternative for the management of patients with large stones in the common bile duct.