Since its first description by Reavan in 1988, accepted criteria for clinical identification of the components of metabolic syndrome have been promulgated by the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) and the World Health Organization (WHO) as well as the International Diabetes Federation (IDF), and the American Association of Clinical Endocrinologists (AACE). Insulin resistance is a common metabolic abnormality underlying type 2 diabetes mellitus and is also an independent risk factor for cardiovascular disease. Although ATP III identified cardiovascular disease (CVD) as the primary clinical outcome of the metabolic syndrome, we now have evidence that metabolic syndrome is associated with type 2 diabetes mellitus, polycystic ovarian disease, nonalcoholic fatty liver disease, and possibly some cancers. This review summarizes evidence in support of the relationship between metabolic syndrome and various cancers and possible underlying mechanisms and therapeutic interventions.