Gallbladder motility was studied by ultrasound in 100 healthy adult volunteers and 150 gallstone patients, in a subgroup of whom gallstone burden, type and number, gallbladder histology and tensiometric responses of gallbladder strips to cholecystokinin octapeptide were evaluated. Patients were divided into contractors (n = 108) and hypocontractors (n = 42), according to their gallbladder motility pattern in vivo. Contractors showed slower gallbladder emptying and increased fasting and postprandial residual volumes, although the ejected amount of bile was greater than that of controls (20.2 +/- SEM 1.1 vs 16.0 +/- 0.7 ml; p < 0.001). In contrast, hypocontractors exhibited slower and less complete gallbladder emptying than controls with a reduction in the absolute amount of ejected bile. Although gallbladder wall inflammation was mild and comparable in specimens from both groups of patients, the thickness of the muscular layer was greater in hypocontractors than in contractors (1073 +/- 76 vs 745 +/- 75 microns, p < 0.01) and related inversely to postprandial ejected volume (r = -0.42; p < 0.03; n = 32) but positively to gallstone volume (r = 0.40; p < 0.03; n = 32). Compared to contractors, gall-bladder muscle strips of hypocontractors exhibited a decrease in frequency and amplitude of spontaneous contraction and in maximal stress and receptor sensitivity to cholecystokinin octapeptide (0.1 nM-1 microM). Postprandial gallbladder evaculation was unaffected by stone number, and by the presence or absence of stone calcification. Gallstone volume was larger in hypocontractors (19.4 +/- 3.0 ml vs 9.6 +/- 0.9 ml, p < 0.001) than contractors. The comparison of in vitro contractility patterns between cholesterol, mixed and pigment stone patients showed a more severe defect in patients with cholesterol and mixed stones than in those with pigment calculi. In conclusion, in gallstone patients: (i) gallbladder motor dysfunction manifests mainly with increased fasting and postprandial residual volumes in contractors and with markedly increased postprandial residual volumes and decreased gallbladder emptying in hypocontractors; (ii) gallbladder kinetics seem to be influenced by stone volume and cholesterol content of calculi but not stone number, calcification or mild chronic cholecystitis; (iii) a form of hypertrophic leiomyopathy is observed in gallstone patients with the most impaired gallbladder motor function.