Public health surveillance constitutes an important activity since it helps in identifying health needs through data collection, and contributes to decision making and actions by analyzing and interpreting data and communicating key results.This paper presents a discussion on the concept of public health surveillance, its objectives and its historical evolution. It deals with the importance of surveillance systems while describing their components and challenges. In addition, the authors point out the importance of administrative data as a relevant source for the surveillance of public health problems, particularly chronic diseases and risk factors.This theoretical discussion leads to the proposal of a conceptual model for surveillance systems, which integrates implementation and evaluation.This article provides a summary of the concept of public health surveillance and underlines the general aspects to be considered by the managers of surveillance systems. It also discusses the use of administrative data for surveillance.