Metabolic syndrome is a constellation of clinical findings that identify individuals at higher than normal risk of developing diabetes mellitus or cardiovascular disease. There are two principal definitions, one emerging from the American National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, and the other from the World Health Organization. Both definitions share the common elements of abdominal obesity, hypertriglyceridaemia, low HDL-cholesterol, hypertension and abnormal glucose regulation. The syndrome is relatively common across continents, and also among those without marked obesity. It is even more common among patients with major mental health disorders such as schizophrenia. Metabolic syndrome can be used to assess risk for cardiovascular disorder and death, and is an alternative to Framingham Risk Calculations. C-reactive protein may play an additional role in risk prediction. Ongoing monitoring for all components of the metabolic syndrome is necessary. Individuals at high risk require multimodal interventions, including lifestyle interventions and targeted medications as appropriate.