Gastroesophageal reflux disease (GERD), an acid-related disease, is usually treated with acid inhibitory drugs including proton pump inhibitor (PPI) according to the clinical practice guidelines for GERD in Japan. However, it is recognized that there are some GERD patients who are resistant to PPI treatment. There are some evidences that various traditional medicines especially for rikkunshito are often combined with Western medicines and prescribed for patients with PPI-refractory GERD at that time. Accordingly, rikkunshito may be useful for treating PPI-refractory GERD via its proper functions such as regulation of gastorintestinal motility and physiological integrity for acid exposure to the esophageal mucosa, because rikkunshito has no inhibitory action on gastric acid secretion.