Overweight/obesity represent a significant public health problem in Canada and abroad. The objective of this paper is to identify potential associations between overweight/obesity and individual as well as socio-environmental determinants. The data sources used are the 2003 Canadian Community Health Survey and the Desktop Mapping Technologies Incorporated database. Geographical Information Systems are first employed to create neighbourhood-level variables such as neighbourhood walkability and fast food accessibility. Multivariate analysis is then applied to estimate the relative effects of individual- and neighbourhood-level risk-factors of overweight/obesity. Results demonstrate the important role of the built-environment after adjustment for demographic, socio-economic and behavioural characteristics. Findings support the rationale that reversing current trends will require a multifaceted public health approach where interventions are developed from the individual- to the neighbourhood-level, with a particular focus on altering obesogenic environments.