Each year, thousands of patients leave Canadian acute care hospitals earlier than their care team recommends. Research shows that such patients are at an increased risk of adverse health outcomes with respect to both morbidity and mortality. They are also more likely to return to hospital, often for the same or a related condition. Using hospital data from the Canadian Institute for Health Information (CIHI) to describe the magnitude of the issue in Canadian acute care and emergency department (ED) settings, this study provides a profile of common characteristics associated with patients who leave against medical advice. It also quantifies the impact of leaving against medical advice on the health care system and on patient outcomes in terms of admission and readmission rates.