Restrictions on non-urgent hospital care imposed to control the 2003 Toronto severe acute respiratory syndrome outbreak led to substantial disruptions in hospital clinical practice, admission, and transfer patterns. We assessed whether there were unintended health consequences to seriously ill hospitalized patients. STUDY DESIGN, SETTING, AND POPULATION: Population-based longitudinal cohort study of patients residing in Toronto or an urban control region with an incident admission for 1 of 7 serious conditions in the 3 years before, or the 4 months during or after restrictions. Short-term mortality, overall readmissions, cardiac readmissions for acute myocardial infarction patients, serious complications for very low birth weight babies, and quality of care measures, comparing adjusted rates across time periods within regions. Mortality, readmission, and complication rates did not change for any condition during or after severe acute respiratory syndrome restrictions. Although rates of invasive cardiac procedures for acute myocardial infarction patients decreased 11-37% in Toronto, rates of nonfatal cardiac outcomes did not change. Restrictions on non-urgent hospital utilization and hospital transfers may be a safe public health strategy to employ to control nosocomial outbreaks or provide hospital surge capacity for up to several months, in large, well-developed healthcare systems with good availability of community-based care.