Background: Radial scanning endoscopic ultrasonography (EUS) has been shown, in experienced hands, to be a safe and accurate means of detecting bile duct stones. We compared linear array EUS with endoscopic retrograde cholangiopancreatography (ERCP), in our first 50 cases, to evaluate efficacy of this examination as well as the learning curve for this indication. Methods: A retrospective study was conducted on 50 patients with suspected choledocholithiasis. We compared results of EUS with those of ERCP as a reference. First a linear EUS examination was performed followed by ERCP, at a median interval of 31 days (range 3 to 162 days). Results: The average age of patients was 56 years (range 26 to 76); 48% were women. Fifteen (30%) had undergone cholecystectomy, a mean of 8.5 years (range 1 to 22) before the EUS. EUS compared with ERCP had a 97% sensitivity, 77% specificity, and 90% accuracy. In 14% of patients EUS provided an additional or alternative diagnosis: chronic pancreatitis (n = 3), duodenitis (2), bile duct stricture (1), chronic gastritis (1). No complications were encountered due to EUS. Conclusions: We found in this early experience that linear array EUS is a reasonably safe and accurate means of detecting choledocholithiasis. Linear array EUS, despite the learning curve, seems to be about equivalent to radial EUS in accuracy. Appropriate use of this less invasive technique may possibly replace the use of diagnostic ERCP. (Gastrointest Endosc 2000;51:51-4.)