Primary care databases extract and combine routine data from the electronic patient records of various participating practices on a regular basis. These databases can be used for innovative and relevant addiction research, but such use requires a thorough understanding of how data were originally collected and how they need to be processed and statistically analysed to produce sound scientific evidence. The aims of this paper are therefore to (1) make a case for why primary care databases should be considered more frequently for addiction research; (2) provide an overview of how primary care databases are constructed; (3) highlight important methodological and statistical strengths and weaknesses of using primary care databases for research; and (4) give practical advice about how a researcher can get access to databases. Three major primary care databases from the UK serve as examples: Clinical Practice Research Datalink (CPRD), The Health Improvement Network (THIN), and QResearch.