Obesity is known to be a major aetiological factor in the development of hypertension. It also leads to dyslipidaemia and raised blood glucose. All of these are components of the metabolic syndrome. Thus, hypertension, as part of the syndrome, is often found together with these other abnormalities. Obesity raises blood pressure by a number of mechanisms, including activation of the sympathetic nervous system and the renin-angiotensin system. Apart from cardiovascular disease and diabetes, the metabolic syndrome is also associated with fatty liver disease, sleep apnoea and some malignancies. Measures to reduce obesity through lifestyle changes are therefore highly desirable, not because of reductions in blood pressure alone.