Oesophageal cancer is one of the most deadly cancers, with typically poor prognosis. In collaboration with groups around the world (Barrett’s and Esophageal Adenocarcinoma Consortium, BEACON, together with collaborators in the UK and Germany), we are conducting large scale gene mapping studies of oesophageal cancer and of the related condition Barrett’s oesophagus. Characterisation of how inherited genetic defects contribute to these conditions may lead to the development of novel therapeutic treatments. We recently showed that the genetic basis of oesophageal cancer overlaps substantially with Barrett’s oesophagus. We have also used genetic data to present strong evidence that some of the known risk factors for oesophageal cancer are causal (rather than being due to confounding or bias).