Data linkage has been defined as 'the bringing together from two or more different sources, data that relate to the same individual, family, place or event'. Australia is one of few countries that has invested significantly in the creation of data linkage facilities.This paper provides an overview of data linkage and its relevance to general practice research.Data linkage enables large-scale studies of whole populations across the healthcare system. Data linkage has been used for studies of health service outcomes and use, epidemiology, and needs analysis. In Australia, there is growing interest in the potential to link data from general practice to other healthcare datasets. This can be achieved through access to Medicare data (Medicare Benefits Schedule and Pharmaceutical Benefits Scheme data) or potentially using data extraction tools to obtain more detailed clinical general practice data. In this article, we discuss issues that relate to privacy and ethical use of data in linkage studies, and provide examples of the types of research performed using this methodological approach nationally and internationally.