Extracorporeal shock wave lithotripsy (ESWL) is a new treatment modality for retained common bile duct stones. Sixty-two patients (mean age 75 years, range 27-95 years) with retained common bile duct stones were treated with two different lithotriptors. One of the lithotriptors operated on the electrohydraulic principle (Dornier HM-3) (n = 13), the other on the electromagnetic principle (Siemens Lithostar) (n = 49). All HM-3 patients were treated under general anaesthesia, whereas with the Lithostar one patients was treated under general anaesthesia, 43 received analgesia and sedation and five had no analgesia at all. Patients treated with the Lithostar had more sessions (mean 1.9 versus 1.3, P less than 0.05) and needed more stock waves (mean 8611 versus 2534, P less than 0.001) than patients treated with the HM-3. Fragmentation was achieved in all patients treated with the HM-3 and in 42 (86 per cent) patients treated with the Lithostar. In this latter group ten patients underwent common bile duct exploration without complications. Eleven patients had transient haematuria after treatment with the HM-3 and two patients (one in each group) had a subcapsular haematoma of the right kidney, all without clinical sequelae. At follow-up (median: HM-3 43 months, Lithostar 18 months), none of the patients had biliary complaints. We conclude that ESWL of retained common bile duct stones in safe and effective with both lithotriptors and should be considered before surgery in the elderly or high-risk patient.