[en] A number of authors have recently evaluated the accuracy of magnetic resonance cholangiopancreatography (MRCP) in the diagnosis of choledocholithiasis at high field strength (1.5 T), but few have specifically addressed the use of MRCP at mid-field strength (0.5 T). The aim of this study was to prospectively compare MRCP at 0.5 T with endoscopic retrograde cholangiopancreatography (ERCP) in the diagnosis of choledocholithiasis. One hundred fifty-two patients with suspected choledocholithiasis underwent MRCP at 0.5 T with two-dimensional (2D) heavily T2-weighted fast advanced spin echo (FASE) and ERCP. MRCP findings were then compared with ERCP findings. ERCP revealed choledocholithiasis in 40 patients (38 at first attempt, 2 after repeat ERCP); the diagnosis was confirmed by endoscopic sphincterotomy or endoscopic papillary dilatation. In all MRCP examinations images of satisfactory quality were obtained. There were 40 true-positives, 110 true-negatives, 2 false-positives, and no false-negatives: a sensitivity of 100% and specificity of 98.2%. This corresponds to a positive predictive value of 95.2% and a negative predictive value of 100%. MRCP at 0.5 T with 2D-FASE, a noninvasive and rapid modality, can accurately diagnose choledocholithiasis. ERCP is indispensable in the treatment of choledocholithiasis, but the diagnostic ability of MRCP with the widely used 0.5 T is adequate, with results similar to those of high field strength. (author)