The pre-operative diagnosis of choledocholithiasis, or common bile-duct stones, is important in patients with cholelithiasis. Intraoperative cholangiography or choledochoscopy followed by exploration of the common bile duct could be limited to those patients with stones, if an adequate pre-operative diagnosis could be made. Many clinicians use pre-operative total alkaline phosphatase level alone or in combination with bilirubin level to determine the presence or absence of choledocholithiasis. Predictive value theory was used to analyze data reported by others to assess the value of alkaline phosphatase level alone or in combination with bilirubin level in identifying patients with choledocholithiasis. The authors conclude that alkaline phosphatase level is not useful either alone or in combination with bilirubin level in determining the presence of common bile duct stones in patients with cholelithiasis.