Previously we reported on the use of laparoscopic ultrasonography in detecting common bile duct stones during laparoscopic cholecystectomy. The aim of this study is to describe the laparoscopic ultrasonographic appearance of the common bile duct mucosa in patients with choledocholithiasis. Medical records of 44 patients with an increased risk for common bile duct stones undergoing laparoscopic cholecystectomy between 1993 and 1998 were reviewed. In the operating room, the laparoscopic ultrasonographic appearance of the common bile duct mucosa was scored in real time as normal, mild changes (hyperechoic mucosa), or severe changes (hyperechoic with mucosal thickening). Of the 31 patients (70%) with stones or sludge in the biliary tree, 29 (94%) had either severe (58%) or mild (36%) hyperechoic and 2 (6%) had normal-appearing common bile duct mucosa on laparoscopic ultrasonography. Of the 13 patients (30%) with no documented stones or sludge, 11 (85%) had normal and 2 (15%) had mild hyperechoic common bile duct mucosa on laparoscopic ultrasonography. Both of these patients had laboratory values indicating recent passage of common bile duct stones. The association between common bile duct stones and the presence of hyperechoic common bile duct mucosa was statistically significant (P < .0001, Fisher's exact test). This is the first report of hyperechoic common bile duct mucosa demonstrated by laparoscopic ultrasonography as a predictor of common bile duct stones. This finding is evident in the majority of patients with common bile duct stones and also may be associated with recent passage of a stone into the duodenum.