Most national and international guidelines for diagnosing hypertension include 24-h ambulatory blood pressure monitoring (ABPM) and self (home) BP monitoring (SBPM) as optional methods for identifying hypertensive patients. However, none of the current guidelines have yet included ABPM or SBPM as fundamental tools for diagnosing hypertension, preferring instead to rely on conventional office readings recorded by mercury sphygmomanometry. During the past 10 years, clinical outcome studies have consistently reported 24-h ABPM and SBPM to be significantly better predictors of cardiovascular events compared with the office BP, even when recorded under "research conditions." Based on the available evidence, the Canadian Hypertension Education Program has now developed an algorithm for diagnosing hypertension that offers three options: 1) conventional office BP, 2) SBPM, or 3) 24-h ABPM. Out-of-office BP measurements are recommended, whenever feasible, to minimize both measurement error associated with mercury sphygmomanometry and the white coat effect experienced by some patients.