The onset of GERD depends on several factors leading to a prolonged exposition of the esophageal mucosa to inflammatory agents. Various mechanisms play a role in different patients, but generally, decreased LES tone and delayed esophageal clearance are the major causes. Although pyrosis and regurgitation are the most frequent complaints, the patient may have different symptoms or can be asymptomatic. The symptoms are not necessarily correlated with damaged mucosa. Recognized complications caused by reflux include esophagitis, stricture, hemorrhage, Barrett's epithelium and ulceration, aspiration and respiratory implications. The severity of complications may be an important element in predicting whether the patient can be successfully treated medically or surgically. The exact knowledge of the pathogenesis is mandatory for carrying out the most effective treatment.