Prevention of disease rather than its alleviation or cure has always been the aim of healthcare professionals. While this goal has been achieved for many infectious diseases through improvements in hygiene and vaccination, as well as for acute deficiency diseases such as scurvy, less progress has been made with chronic diseases. These are increasing as the population ages. Chief among the chronic diseases on the increase are: Type 2 diabetes. Hypertension and cardiovascular disease, which are responsible for over 40 per cent of all deaths in the UK (DoH 1999). Obesity, which is a major cause of morbidity and predisposes to diabetes, cardiovascular disease and other chronic illnesses. Cancer. This article describes the nature, aetiology and prevention of the metabolic syndrome. Although not a disease, the metabolic syndrome is like smoking in that it strongly predisposes to disease and is preventable.