As real-time ultrasonography is a cheap, noninvasive, relatively easy, validated and reproducible technique, it can be repeated over time to document time-related changes of gallbladder motor function. Ultimately, functional ultrasonography estimates gallbladder shape and volume in fasting state and in response to a test meal (liquid or mixed solid-liquid, provided there is sufficient fat content) or exogenous stimulus (e.g., i.v. cholecystokinin or ceruletide). Although functional ultrasonography of the gallbladder has been mainly used for research purposes in specific referral centres, its simplicity makes such a technique appealing in the clinical setting to assess gallbladder motor function in both health and disease. Indications include the study of healthy subjects and of patients during pathophysiologically relevant conditions; in particular when subjects are at risk for gallbladder stasis and gallstone disease or during gallstone disease when a decision concerning medical dissolution therapy is required.