This study deals with the diffusion of a new medical technology — vaccination against smallpox — in nineteenth-century Scania in Sweden. Using an aggregated sample of parishes as well as a micro-level dataset for four parishes, we investigate the socioeconomic as well as the geographical patterns of diffusion of vaccination in the province. We also relate the adoption of vaccination across geographical areas, as well as across social groups, to the availability of information, ability to acquire and process this information, and to levels of social capital and trust in society. Our results point to the conclusion that while vaccination spread very quickly geographically after its introduction, there were considerable differences between social groups. The better situated, betted educated, landholding peasants were more ready to adopt the new technology of smallpox vaccination. This had little to do with better access to economic resources as vaccination in general was provided free of charge. Instead we hypothesize that it was related to a higher ability to acquire and utilize the information available, and/or a higher level of trust in the authorities among these peasants.