Abstract
Pharmacoepidemiology is the study of the use and effects of medications in populations. Large health care databases are often used to address research questions within pharmacoepidemiology. This paper briefly describes the kinds of research questions that can be addressed using pharmacoepidemiology databases, provides an overview of pharmacoepidemiologic databases, describes some differences between medical records and administrative databases, discusses factors that should be considered when choosing a database for a particular study, and considers what the future holds.