One of the etioloic factors in the formation of cholesterol gallstones is the supersaturation of gallbladder bile with cholesterol. However, this factor does not complete the explanation. The bile stasis in the gallbladder may also play a role in the formatior: of the cholesterol gallstones by supplying the time for nucleation of cholesterol crystal. The present study evaluated the gallbladder emptying in response to a fatty meal by ultrasonography in 11 patients with asymptomatic gallstones and normal control group of 13 healthy subjects. Of the eleven pa- tients with gallstones, five had radiolucent stones and six had radioopaque stones. Additionally, we also evaluated the effect of nifedipine, calcium channel blocker, on gallblad- der contraction in both patients with gallstones and control group. The gallbladder was significantly contracted in control group by the fatty meal but not by water(p<0.01). The contraction of gallbladder by fat meal in gallstone group was significant- ly decreased comparing with that in control group(p<0.01). The time of maximum contrac- tion was delayed in patients with gallstones. Dividing the patients with gallstones into the ra- diolucent stones and the radioopaque stones, the more significant decrease of gallbladder con- traction was noted in patients with radiolucent stones than in those with radioopaque stones(p <0.05). The gallbladder contraction in patients with gallstones and control group was signifi- cantly blocked with a pretreatment of oral nifedipine(p<0.01). In conclusion, the more significant decrease of gallbladder contraction in patients with radio- lucent stones may be interpretated as the possible factor of pathogenesis for the formation of the cholesterol stone. Additionally, the calcium ion may be related to gallbladder contraction, and nifedipine could lessen the gallbladder contract,ions in both controls and patients with gall- stones.