Omeprazole, a proton pump inhibitor, is widely used for the treatment of patients with peptic ulcer, gastroesophageal reflux disease and functional dyspepsia (FD), although some studies have demonstrated that omeprazole delays gastric emptying. The purpose of this study was to investigate the efficacy of omeprazole on gastric motility including gastric myoelectrical activity and gastric emptying. This study was performed on 12 healthy volunteers. Gastric motility was evaluated with cutaneously recorded electrogastrography (EGG) and gastric emptying of semi-solid meals using the (13)C-acetic acid breath test. EGG and gastric emptying were measured before and after treatment with 20 mg omeprazole orally for 7 days. In the fasting state, the percentage of EGG normogastria increased significantly compared to the baseline. No significant changes were observed in other EGG parameters including the percentage of tachygastria and bradygastria in both fasting and postprandial states, and the power ratios between both before and after ingestion of omeprazole. In addition, administrated omeprazole did not show any significant differences in the gastric emptying parameters such as the half emptying time. We conclude that administration of omeprazole did not affect gastric motility but improved gastric myoelectrical activity. These effects of omeprazole may be one of the mechanisms involved in its efficacy in relieving dyspeptic symptoms in FD patients.