Gastroesophageal reflux disease (GERD) is a highly prevalent disease, especially in Western countries. Its pathophysiology is complex and multifactorial. The intricate valvular mechanism at the level of the esophagogastric junction (EGJ) is responsible for preventing the return of food and gastric contents to the esophagus, composing a barrier that balances the transdiaphragmatic pressure gradient (positive intra-abdominal pressure and negative intra-thoracic pressure). GERD occurs when there is a disbalance between these two forces. Some clinical conditions may affect this balance leading to GERD development such as: hiatal hernia, esophageal and gastric dysmotility, obesity and restrictive pulmonary disease. Therefore, to provide proper therapy it is essential to comprehend GERD pathophysiology.