The metabolic syndrome is a cluster of interrelated common clinical disorders, including obesity, insulin resistance, glucose intolerance, hypertension, and dyslipidemia (hypertriglyceridemia and low HDL cholesterol levels). According to recently defined criteria, the metabolic syndrome is prevalent and is associated with a greater risk of atherosclerotic cardiovascular disease than any of its individual components. Primary defects in energy balance that produce obesity (and visceral adiposity in particular) are sufficient to drive all aspects of the syndrome. Increased free fatty acids and lipid accumulation in certain organs are mediators of insulin resistance. Obesity also leads to a proinflammatory and prothrombotic state that potentiates atherosclerosis. Pathways leading directly from adiposity to the genesis of dyslipidemia and hypertension have been elucidated. Recent knowledge implies a role for fat-derived "adipokines," including TNF alpha and adiponectin, as pathogenic contributors or protective factors. Current therapies include diet and exercise as well as agents indicated for the treatment of individual components of the syndrome. Future therapies may accrue from the aggressive pursuit of newer molecular drug targets that have the potential to prevent or treat multiple aspects of the metabolic syndrome.