Aim: In this article the authors illustrate using a case study approach how primary care professionals can use the combination of geodemographic data with hospital episode statistics (HES) to predict the location of people ‘at risk’ of diabetes mellitus (Type 2 diabetes) in the population of England. This approach facilitates social marketing of those ‘at risk’. Method: Geodemographic segmentation data for all households was combined with HES for 2001–2002, to predict population groups ‘at risk’ of Type 2 diabetes. Using a case study approach and quantitative data analysis techniques, a profile of the undiagnosed and ‘at risk’ population of Slough Primary Care Trust was created at town, ward and street levels. Recent literature on social marketing was applied to predicate a discussion of the theory and practice of social marketing that was most likely to succeed in dealing with the prevention of Type 2 diabetes, via the reduction of obesity and overweight in the population. Discussion: The increase in lifestyle-related diseases, such as, Type 2 diabetes that are linked with the rise in overweight and obesity and create large disease management costs for the National Health Service (NHS) are of great concern to primary healthcare professionals and governments throughout the westernized world. Until recently, public and government responses have been very reactive in respect of population groups most in need of lifestyle change. Approaches to the identification of ‘sub-populations’ most at risk of Type 2 diabetes and targeting of these is of direct relevance to the preventive work of primary care professionals. Conclusion: Geodemographic data overlaid onto official NHS and other routinely collected data, can aid the identification and targeting of groups most vulnerable to overweight and obesity, through social marketing approaches including direct mail, telephone canvassing and door-to-door communication channels.