Gastroesophageal reflux disease (GERD) is highly prevalent in Western countries, particularly when considering its most classic symptom that is heartburn. This symptom is very frequent in the community and ranges from 10% to more than 30%, according to the various population-based studies. This disease is much more represented in Europe and USA than in Asiatic countries. It has been shown that GERD prevalence increases in parallel with the remarkable growth of obesity, as this condition is able to favor all the pathogenetic mechanisms leading to it. Current information regarding the phenotypic presentation of GERD shows that there are two main phenotypic manifestations, that are erosive reflux disease (ERD) and non-erosive reflux disease (NERD) and the latter includes the majority of patients (up to 70%). The major complication of GERD is the development of Barrett esophagus, a pre-malignant lesion potentially leading to esophageal adenocarcinoma. Data from medical literature on the natural history of this disease are scant and mainly retrospective, so the interpretation of them is very difficult. However, they seem to suggest that both NERD and mild esophagitis tend to remain as such overtime and the progression from NERD to ERD, from mild to severe ERD and from ERD to Barrett's esophagus may occur only in a small number of cases, ranging from 0% to 30%, 10-22% and 1-13%, respectively. Future studies should help us in elucidating better the real transition from one category to another and to do this, we have to exclude from the world of GERD all the functional conditions that nowadays can be easily recognized by means of impedance-pH monitoring.