The insulin resistance syndrome consists of the co-occurrence of metabolic risk factors for type 2 diabetes and cardiovascular disease, including overall obesity, central obesity, dyslipidemia (characterized by elevated levels of triglycerides and low levels of high-density lipoprotein cholesterol), hyperglycemia, and hypertension. Using criteria proposed by the National Cholesterol Education Program Adult Treatment Panel III, national survey data suggest the insulin resistance syndrome is very common, affecting about 24% of US adults aged greater than 20 years. The syndrome is more common in older people and in Mexican Americans, and will increase in prevalence as populations age and become more obese. Identification of the syndrome warrants aggressive interventions known to prevent type 2 diabetes and cardiovascular disease, including weight reduction, increased physical activity, and control of hypertension and dyslipidemia.