Renal artery stenosis (RAS) is a common disease with complex treatment implications. Patients with RAS face high short- and long-term risks for cardiovascular events, including stroke, myocardial infarction, unstable angina, congestive heart failure and death. Unfortunately, scant evidence exists regarding the impact of medical therapy on the prognosis of this condition. Investigators will conduct a comprehensive population-based analysis of medical therapy for RAS by examining the effects of three distinct medications: angiotensin modulators, beta blockers and statins. Based on administrative data, this work will be the largest study of reno-vascular disease ever undertaken, with a probable sample size of more than 13,000 patients. The study will provide important data on the epidemiology and prognosis of RAS in the ethnically diverse Ontario population.