Gallstone diseases appear frequently in surgical patients. One of the etiolic factors in the formation of cholesterol gallstones is the supersaturation of bile with cholesterol. The bile stasis in the gallbladder may also play a role in the formation of cholesterol gallstones by supplying the proper condition to nucleation of cholesterol crystal. Author evaluated gallbladder empting in response to fat meal by ultrasonography in 12 patients with gallstones and normal control group of 12 healthy subjects. Of the 12 patients with gallstones, six had radiolucent stones and the rest of them had radioopaque stones. Additionally, author evaluated gallbladder contraction in both cholesterol gallstones and pigment gallstones. The gallbladder was significantly contracted in control group by the fat meal but not by water. The contraction of gallbladder by fat meal with gallstone patients was significantly decreased compared with those in control group. The time of maximum contraction was 30 minutes in patients with gallstones. At 30 minutes, the gallbladder contraction was more significantly decreased in patients with radiolucent stones than in those with radioopaque stones. In conclusion, the more significant decrease of gallbladder contraction in patients with radiolucent stones may be interpretated as the possible factor of pathologenesis for the formation of the cholesterol stone.