There are many important reasons why Canadian paediatricians, paediatric subspecialists and health-care providers actively participate in the Canadian Paediatric Surveillance Program (CPSP). Among these reasons is the timely epidemiological prospective data collection that has a direct impact on the diagnosis and treatment of patients. Surveillance of rare genetic conditions may identify populations at risk, which in turn, may lead to implementation of population-based screening programs. Such programs allow for intervention at younger ages, thereby improving quality of life. Data collection can monitor the incidence of disease before vaccination as well as the effectiveness of immunization programs.