Recent epidemiological studies indicate that exposure to polychlorinated biphenyls (PCBs) is associated with an increased risk of metabolic syndrome, a group of disorders that includes obesity, glucose intolerance, high cholesterol, and hypertension. Metabolic syndrome increases the risk of developing type 2 diabetes. PCBs accumulate in adipocytes, which are known to play a key role in the genesis of metabolic syndrome. Recently generated extended lifespan human pre-adipocytes will provide a unique opportunity to assess the short and long term effects of PCBs on adipocyte biology. These cells will be used to test the hypothesis that exposure of adipocytes to PCBs causes long-term effects on gene expression to alter adipocyte differentiation and function. This study will lead to further understanding of how PCBs cause metabolic syndrome, may provide useful biomarkers for assessment of disease risk, and could point to new targets for therapy.