BACKGROUND: Adenocarcinomas of the oesophagus and proximal stomach are the most rapidly increasing malignancies in some countries; however, there are no comparative studies on global disease incidence, and the relationships between these two malignancies are undefined. METHODS: We evaluated the cumulative rates and age-specific incidence rates per 100 000 population for adenocarcinomas of the oesophagus and proximal stomach for all countries in the Cancer Incidence in Five Continents database, and compared them with rates for oesophageal squamous cell carcinoma. RESULTS: Substantial variations in cumulative cancer rates were found between genders, between countries, between different ethnicities within the same country, and within the same ethnicity residing in different countries. Cumulative rates (ages 0-74 years) for oesophageal adenocarcinoma varied from 0 (e.g. Thailand) to 0.6 (Scotland, males, 95% CI : 0.56, 0.64); for proximal stomach cancer from 0 (Singapore, Malay females, 95% CI : -0.01, 0.11) to 0.52 (The Netherlands, males, 95% CI : 0.49, 0.55); and for oesophageal squamous cell carcinomas from 0 (non-Jews in Israel, females) to 1.84 (Brazil, Porto Alegre, males, 95% CI : 1.42, 2.26). There was a continuous increase in age-specific incidence rates with advancing age for oesophageal/proximal stomach adenocarcinomas, but a decrease in age-specific incidence rates for oesophageal squamous cell carcinoma after age 75 years. The cumulative rate trends for adenocarcinomas of the oesophagus and proximal stomach were often dissimilar, and varied by country, gender, and ethnicity. CONCLUSIONS: These results suggest that different risk factors may be associated with adenocarcinomas of the oesophagus versus the proximal stomach; the marked rate variation implies a substantial environmental component to the recent incidence changes.