Scintigraphic measurement of gastric emptying time has been reported to be influenced by the variation in depth of radionuclide within the stomach. In order to determine the effect of tissue attenuation in the measurement of gastric emptying time, 15 gastric emptying studies were performed with Tc-99m labeled egg sandwiches. Single anterior detector method overestimated the T1/2 by an average of 13% than geometric mean method and range of overestimation was wide (from -13% to 132%). Therefore, to evaluate the gastric empthying time accurately, methods of attenuation correction are needed.