Oesophageal and gastric cancer patients have a poor survival rate and the aetiology of these cancers is largely unclear and understudied. These tumours are hypothesized to have distinct aetiologies within histologic subtypes and subsites; yet few studies have been of sufficient size to investigate these subtypes. Observational evidence suggests that these tumours may be linked to variation in endocrinologic pathways. The aim of this study is to investigate hormones and hormone-related factors in relation to oesophageal and gastric cancers by subtype and subsite by prospectively examining lifestyle, behavioural and biochemical data. The specific aims are to: 1) Investigate anthropometric and reproductive factors; 2) Examine serum levels of sex hormones, appetite/digestive hormones, and insulin/IGF-axis components. This study has direct translational potential by using the data generated to identify specific risk factors that can be used to identify individuals who would most benefit from interventions and more targeted screening and surveillance programs.