Objective. Endoscopic mechanical lithotripsy is frequently used to overcome the difficulties of removing large bile duct stones endoscopically. The aim of this study was to identify predictors of endoscopic mechanical lithotripsy failure. Material and methods. One hundred and thirty-four patients who underwent mechanical lithotripsy for difficult choledocholithiasis were evaluated retrospectively. Predictive factors of outcome and procedure-related complications were analyzed. The clinical outcomes of subsequent management were also evaluated in cases of unsuccessful endoscopic mechanical lithotripsy. Results. Endoscopic mechanical lithotripsy was successful in 102 patients (76.1%). Stone impaction, size (≥30 mm), and the stone size to bile duct diameter ratio (>1.0) were significant predictors of endoscopic mechanical lithotripsy failure, with estimated odds ratios of 17.83, 4.32 and 5.47, respectively. There was no difference in complication rates between the successful and failed mechanical lithotripsy groups. When mechanical lithotripsy failed, all patients were successfully treated using various modalities, including surgery, without mortality. Conclusions. An impacted stone, stone size (≥30 mm) and stone size to bile duct diameter ratio (>1.0) were predictors of failure of endoscopic mechanical lithotripsy for a difficult bile duct stone. Alternative approaches should be considered in patients with predictors of unsuccessful endoscopic mechanical lithotripsy in order to avoid wasting time and resources.