The use of data from medical-administrative databases and the linking of these databases form the foundation for the development of chronic disease surveillance in Quebec and Canada. By using the unique identifier assigned to every resident of Quebec, it is possible to link medical-administrative databases and determine both service utilization and the diagnoses associated with each individual’s health status. Based on this principle, case definitions are formulated and algorithms are developed to identify all prevalent cases and create a database covering one or more chronic diseases. It is then possible to calculate a series of indicators that track disease trends over time and the associated service utilization. Naturally, this passive surveillance has limitations since it cannot account for individual risk factors. Furthermore, validating the case definition is a significant and unavoidable methodological challenge. However, the surveillance model is an essential tool for the Quebec healthcare system. (R.A.)