Gastroesophageal reflux disease is increasing worldwide. The causes of reflux symptoms are not found exactly. especially, the postprandial reflux symptoms are more common than the all day reflux symptoms. One of the causes of reflux symptoms is the relaxation of the lower sphincter of the esophagus. But, the sphincter relaxation also occur in normal people. But, there is a difference in postprandial reflux pattens between the patients and the normal people. So, in this study, we want to compare the difference of reflux pattern between the patients who have postprandial reflux symptoms and normal people though the 24hr pH monitoring.

Inclusion Criteria:

1. over 19 years old, male and female
2. normal people (control group, who has no postprandial reflux symptoms
3. patients who have postprandial reflux symptoms (postprandial reflux symptom means that within the last 6 months, postprandial reflux symptoms more than once a week for more than 1 month)

Exclusion Criteria:

1. patients who have nasoesophageal stricture
2. patients who have bleeding tendency
3. patients who have esophageal varix
4. patients who have cardioverter implantation
5. patients who had surgery for esophagus, stomach or duodenum
6. patients who are taking medications, gastrointestinal motility drugs