Left ventricular hypertrophy is a common manifestation of systemic hypertension and a strong independent risk factor for adverse cardiovascular events and death. This article reviews studies that have defined the strength and scope of the association between increased left ventricular mass and prognosis, techniques of measuring left ventricular mass, and mechanisms believed responsible for left ventricular hypertrophy. Recent data suggesting the benefit of left ventricular mass reduction during hypertension treatment and the role of echocardiography in assessing patients with elevated blood pressure are discussed.