Hemovigilance systems are important programs for: monitoring trends of known risks; evaluating effectiveness of steps taken to reduce risks; providing data to support recommendations for change and guideline development; and contributing overall to the safety of transfusion. The Transfusion Transmitted Injury Surveillance System is the hemovigilance system implemented in Canada. It evolved in 1999 as a pilot program and expanded across Canada in 2005. Each province reports their adverse reactions to the transfusion of blood products and plasma proteins to the Public Health Agency of Canada (PHAC) at predetermined intervals. PHAC reconciles, summarizes the data and publishes a report approximately 2 years after the data are collected. This is considered a passive reporting system but in spite of the delays, the program provides useful information to address a variety of questions. Examples include: assessing the impact of a provincial patient transfusion history registry in Québec on reporting of hemolytic transfusion reactions; identifying trends of bacterial contamination of blood products and assessing the impact of interventions on these events; and the impact of male-only plasma on the incidence of Transfusion Related Acute Lung Injury. Although hemovigilance data has been successfully used to improve blood safety, we must continue to explore ways to utilize such data to improve and implement safe transfusion practices.