The incidence of adenocarcinoma of the esophagogastric junction has increased rapidly in the later half of the twentieth century in the United States and most western countries. Although squamous cell carcinoma of the esophagus used to predominate, adenocarcinoma of the distal esophagus and esophagogastric junction now accounts for more than half of new diagnoses in western countries. There also has been a shift from the development of distal gastric cancers to ones in a more proximal location. These recent epidemiologic shifts have led to controversy regarding the etiology and treatment of adenocarcinoma of the esophagogastric junction. Uncertainty still exists with regards to nomenclature and classification, risk factors, treatment, and screening and surveillance of esophagogastric adenocarcinoma. This article examines the epidemiology and etiologies of adenocarcinoma of the esophagogastric junction.