Fifty-three patients with biliary symptoms were studied at least four years after cholecystectomy by isotope techniques. There was a highly significant correlation between symptoms and disturbances of bile flow, such as dyskinesia or obstruction. There was no correlation with serum enzyme levels such as gamma-GT, alkaline phosphatase, bilirubin or transaminases. Measurements of the diameter of the bile duct on cholangiograms provided no evidence of obstruction up to 15 mm., although a diameter in excess of 10 mm, made obstruction likely. The upper value for "normal" bile flow derived from hilar flow curves of patients without dyskinesia showed a half value period of 27.5 minutes. The disturbances of flow demonstrated by isotope methods in the presence of typical symptoms, and without other pathological findings, indicate a pre-clinical stage of a partly compensated bilio dynamic insufficiency. Where there is no morphological evidence of biliary obstruction, one must assume inflammatory changes round the papilla of Vater; these are frequent even in normal biliary tracts and almost always present after cholecystectomy. Quantitative hepato-biliary scintigraphy is the most reliable method for objective measurement of disturbances of bile flow and make it possible to avoid the vague diagnosis of "post-cholecystectomy syndrome".