Metabolic syndrome is defined as an association of central obesity and several other cardiometabolic risk factors. Dysfunctional visceral adipose tissue and inflammatory status appear to be involved in its genesis. New definitions have decreased the threshold for glycaemia and one has lowered the threshold for waist circumference, leading to an increase in the prevalence of metabolic syndrome. However, the impact on mortality with these new definitions is lower than with the National Cholesterol Education Program-Adult Treatment Panel III 2001 definition. An increase in waist circumference, along with increased glycaemia, triglycerides and/or blood pressure is more highly associated with an increased risk of mortality than are other associations, while a decrease in high density lipoprotein cholesterol increases risk of coronary heart disease. The risk of sudden death and stroke is particularly notable with metabolic syndrome. Metabolic syndrome is associated with an increase in heart rate, pulse pressure, arterial stiffness and left ventricular hypertrophy, impairment of diastolic function, enlargement of the left atrium and atrial fibrillation. In the 2007 European recommendations for the management of high blood pressure, metabolic syndrome is now taken into consideration for both risk stratification and in selecting the optimal therapeutic strategy for arterial hypertension.