The metabolic syndrome refers to the co-occurrence of several known cardiovascular risk factors, including insulin resistance, obesity, atherogenic dyslipidemia and hypertension. These conditions are interrelated and share underlying mediators, mechanisms and pathways. There has been recent controversy about its definition and its utility. In this article, I review the current definitions for the metabolic syndrome and why the concept is important. It identifies a subgroup of patients with shared pathophysiology who are at high risk of developing cardiovascular disease and type 2 diabetes. By considering the central features of the metabolic syndrome and how they are related, we may better understand the underlying pathophysiology and disease pathogenesis. A comprehensive definition for the metabolic syndrome and its key features would facilitate research into its causes and hopefully lead to new insights into pharmacologic and lifestyle treatment approaches.