Data on all patients 65 years or older who were admitted for a first CHF diagnosis in the province of Quebec, Canada, between January 1, 1998, and March 31, 2007, were obtained from the hospital discharge summary database of Quebec and the provincial physician and drug claims databases. All patients had CHF recorded as the primary diagnosis (International Classification of Diseases, Ninth Revision, code 428). Patients were included in the cohort if they had a first CHF-related hospital admission, were discharged alive, and filled prescriptions for an ACE inhibitor (captopril, cilazapril, enalapril, fosinopril, lisinopril, perindopril, quinapril, ramipril, and/or trandolapril) or ARB (candesartan, eprosartan, irbesartan, losartan, telmisartan, and/or valsartan) after discharge. Follow-up for each patient was from the time of first prescription filled for any ACE inhibitor or ARB (time 0) to the time of death, CHF readmission, end of the study period, or switch to a different drug class. Three study groups were formed according to the initial dose of ACE inhibitor or ARB prescribed: low-, medium-, and high-dose groups.