While mechanism of functional dyspepsia is unclear, treatment has also been far from satisfactory. Proton pump inhibitor has been recommended as the first line treatment for functional dyspepsia and it has been shown that the use of PPI is associated with a 14% reduction in risk of persistent dyspepsia compared to placebo. However, the mechanism of symptom relief is unclear. While PPI exerts its effect primarily through suppression of acid-induced symptoms, recent studies have shown that PPI may affect gastric motility function such as gastric volume, gastric emptying and trigger of migratory motor complex. Most of these studies were performed on healthy volunteers who received only a very short course of PPI. The correlation between symptom and gastric emptying is lacking in these studies.