Simultaneous studies of gastric emptying by ultrasound and scintigraphy were performed in 14 subjects to assess the use of ultrasound for the measurement of gastric emptying rate. The presence of air in the stomach prevented the acquisition of gastric emptying data by ultrasound in 3 of the 14 subjects. In the remaining 11 subjects there was no significant difference between values for the half-time (t1/2) of gastric emptying obtained by scintigraphy [for anterior imaging, mean t1/2 = 20.9 +/- 9.9 min (+/- SD); for anterior and posterior imaging, geometric mean t1/2 = 21.1 +/- 10.5 min (+/- SD)] compared with those derived by ultrasound [mean t1/2 = 20.2 +/- 10.0 min (+/- SD), p greater than 0.05 for each comparison]. A significant correlation between the t1/2 of gastric emptying derived by scintigraphy (anterior scanning and geometric mean of counts obtained by anterior and posterior scanning) and the t1/2 measured by ultrasound was obtained (r2 = 0.7, 0.69, respectively). These results imply that ultrasound can be used for the valid assessment of the gastric emptying rate in humans.