In order to elucidate the effects of various gastrokinetic drugs on gastric emptying and the sites of their action in the stomach, changes in gastric emptying after administration of these drugs were determined in healthy adults by means of radioisotopic technique, by setting 3 regions of interest, i.e., the whole stomach, the proximal area and the antral area. Following results were obtained. 1. With metoclopramide administration, no particular movement of gastric contents was found for several minutes after ingestion. Once the movement of emptying was initiated, the gastric contents were transferred more efficiently from the proximal area to the antral area in comparison with the corresponding movement observed in persons given no metoclopramide. On the other hand, the outflow from the antral area to the duodenum exceeded the inflow from the proximal area to the antral area. 2. With domperidon administration, transfer of gastric contents was markedly increased, but the outflow from the antral area did not exceed the inflow. Domperidone caused overall facilitation of gastric emptying, mainly by enhancing the emptying movement in the proximal area. 3. With aclatonium napadisilate administration, marked transfer of the gastric contents from the proximal area to the antral area was noted, and the outflow from the antral area to the duodenum was equal to the inflow within 10 min, then exceeded the inflow. 4. With trimebutine maleate administration, transfer of gastric contents from the proximal area to the antral area was conspicuous, and the outflow from the antral area exceeded the increased inflow, resulting in overall faciliation of gastric emptying.