Gastroesophageal reflux disease (GERD) is a common disease frequently encountered by surgical pathologists. Although the pathogenesis and clinical features of the disease have been studies for years, many unanswered questions remain. Typical clinical symptoms along with the endoscopic findings, pH monitoring, and biopsies, all support the diagnosis. However these tests may yield conflicting findings, and at present there is no gold standard for the diagnosis of GERD. In patients with normal or nearly normal endoscopic findings (nonerosive reflux disease), the major diagnostic burden lies with the histology. The histologic diagnosis of GERD is based on a combination of findings, including basal cell hyperplasia, papilla elongation, inflammation, and dilatation of intercellular spaces. However, these features exhibit varying sensitivity and specificity, and minimal biopsy criteria for the diagnosis of reflux esophagitis have not been rigorously tested in well-characterized patient populations. However, given the high prevalence of GERD, pathologists face esophageal mucosal biopsies daily and must recognize the diagnostic strengths and limitations of histologic features of reflux esophagitis. Future studies and new techniques may improve the diagnostic strength of histology and establish meaningful minimal criteria for the diagnosis of reflux esophagitis.