Among the various methods used to measure gastric emptying time, scintigraphy is nowadays the technique of choice. Since only few data are available on the operative characteristics of the method, the authors investigated reproducibility, sensitivity, and specificity of a modified scintigraphic technique for the measurement of gastric emptying time. Three groups of subjects--healthy volunteers, patients with functional dyspepsia, and patients with upper gastrointestinal conditions--were administered liquid meals having various standard consistencies (349 tests on the whole). In both healthy volunteers and dyspeptic patients the method had high sensitivity (72%), good specificity (69%), and low intra-subject variation (25%). In all cases, the increase in meal density produced a delay in gastric emptying. Dyspeptic patients had slow gastric emptying of high-fiber meals, while in duodenal ulcer and in atrophic gastritis emptying was significantly faster. The radionuclide method proved valuable in measuring gastric emptying and was useful to confirm the pathogenesis of the various conditions. As for functional and organic pathologic conditions, it allowed treatment efficacy to be evaluated.