Hiatal hernia is a very common finding in esophagogastroduodenoscopy (EGD). Only some patients with hiatal hernia suffer from gastroesophageal reflux disease (GERD), defined by pathological 24-h-pH-metry, while almost all patients with GERD do have hiatal hernia. To work out the differences in possible motility disorders and in a pathologic acid reflux we examined 92 patients with hiatal hernia by means of manometry and 24-h-pH-metry of the esophagus. A motility disorder of the tubular esophagus in the patients with GERD (with or without reflux esophagitis) was significantly more common than in patients without GERD (p = 0,006). In most cases it was an esophageal hypomotility. There is no significant difference in the basal pressure of the lower esophageal sphincter (LES) between the two groups. We conclude that besides other factors which impair esophageal clearance function a motility disorder of the tubular esophagus is the main cause for the development of GERD in the patients with hiatal hernia. A lowered pressure of the LES seems not to play a maior role in the etiology of reflux esophagitis.