Genetic and epigenetic epidemiology are rapidly developing aspects of population-based health research that have clear translational potential. These endeavours both benefit considerably from extensive international collaborations. Establishing robust associations between genetic variation and common complex disease phenotypes requires very large sample sizes than can only realistically be generated through collaborative work. Furthermore, exploring associations in populations with different historical origins contributes to location of functional variation. Interactions of genetic variation and environmental exposures are best studied against a background of widely different environments, something that is best leveraged between, rather than within, countries. Epigenetic patterns are clearly influenced by exposures such as 1-carbon composition of the diet that differ between countries, allowing considerably greater power for establishing associations. Triangulating environmental exposures, genetic variation and epigenetic mediation offers to provide a step-change in ability to detect causal associations, of direct relevance to therapeutic and preventive activities. GeoCoDE will assemble a group of investigators who are custodians of world-leading population resources, have access to appropriate technologies and have been involved in advancing methods of data analysis. Through exchange visits of senior and junior research staff, workshops and extensive networking we will contribute to major advance in European capacity in this field.