Barrett’s esophagus occurs when the normal cell type that lines the lower part of the esophagus (squamous cells) is replaced by a different cell type (intestinal cells). This process usually results from repetitive damage to the esophageal lining. The most common cause of this is longstanding gastroesophageal reflux disease (GERD), a condition in which the esophagus is exposed to excessive amounts of stomach acid. Interestingly, the intestinal cells of Barrett’s esophagus are more resistant to acid than squamous cells, suggesting that they may be an adaptation to the chronic acid exposure. The problem with this adaptation is that the intestinal cells have a small potential to transform into cancer cells.