Background: Ultrasound (US) examination of gallbladder is considered to be reliable, both in morphological and functional evaluation. We used US to study the gallbladder of a series of centenarians in order to show the characteristics of this organ in these subjects. We then compared the data obtained with two control populations omposed of elderly and adult subjects, respectively. Methods: US examination was done after an overnight fast and after emptying the gallbladder at 15-min intervals for a period of 90 min. To induce emptying of the gallbladder, we chose a semisolid meal with a small caloric value (370 kcal). The following parameters were evaluated: fasting gallbladder volume (in milliliters) before administration of the meal (considered to be 100%); gallbladder emptying (according to the formula: fasting gallbladder volume minus post-meal gallbladder volume at 10-min intervals divided by fasting gallbladder volume: the result of this operation was multiplied by 100); gallbladder motor functions, such as ejection volume (ml), is considered as the difference between fasting gallbladder volume and residual volume; ejection fraction (%), considered as the difference between fasting gallbladder volume and residual volume, is expressed as percentage fasting volume; and ejection rate (%/min) is calculated by dividing ejection fraction by time requested to reach the residual volume. Results: We found a common bile duct diameter that was significantly higher in centenarians than in the elderly and adults. Gallbladder wall thickness was significantly higher in centenarians than in adults. We also found substantially significant differences between centenarians with and without gallstones and elderly and adult subjects in the following parameters: mean gallbladder volume (reduced), residual volume (reduced), ejection volume (reduced) and ejection rate (reduced). The differences were not significant for the ejection fraction, and they were slightly reduced in centenarians compared to the other groups. There was a negative correlation between age and axial length (transverse diameter), age and width and age and common bile duct (CBD) diameter in the elderly group only. Conclusions: The study of gallbladder function in elderly people and centenarians is important because this parameter is related to the quality of digestion and absorption of many alimentary substances as well as to the formation of cholesterol gallstones. We found that gallbladder functions in centenarians are almost normal with respect to the elderly and adults. Contractility was higher than in our elderly sample. This fact ensures a correct concentration of bile salts and a good intestinal transit rate. It may represent one of the factors allowing for good digestive function in these subjects, which contributes to their health status.