The precise causes of esophageal cancer have not been identified. A number of carcinogens and predisposing conditions have been implicated. There are pronounced differences between the demographic groups affected by squamous cell carcinoma and adenocarcinoma of the esophagus. Whereas the incidence of squamous cell carcinoma has remained constant, the incidence of adenocarcinoma of the esophagus has been rising steadily in recent years. The reasons for this trend remain unclear. Further studies of the molecular biology and epidemiology of this disease are needed.