Infectious disease surveillance in Quebec draws on both European and American traditions, reflecting the history that has shaped Quebec today. Over the years, the concept of surveillance has evolved in light of advances in epidemiology and statistics, as well as new information and communication technologies. The fundamental objective of surveillance, however, remains the continuous analysis of data relevant to decision-making and action in public health. Infectious disease surveillance relies on a public health network modeled after the healthcare system; surveillance practices are governed by the Public Health Act. While retrospective descriptive analysis of Notifiable Diseases (Mado) used to be the mainstay of the practice, we are now expected to anticipate emerging trends in real time. The scope of surveillance has broadened, real-time monitoring is now a reality, and new challenges are linked to the relevance of data that is often less specific and to the accurate interpretation of results obtained through increasingly sophisticated methodologies. This article provides an overview of the various components of infectious disease surveillance in Quebec, the evolution of the role, and the ever-changing challenges posed by daily practice. (R.A.)