Plasminogen activator inhibitor-1, a member of the serine protease inhibitor (serpin) superfamily, is the principal inhibitor to tissue-type plasminogen activator and urokinase-type plasminogen activator. Elevated plasma PAI-1 levels, an independent cardiovascular risk factor, has been shown to be a predictor of recurrent myocardial infarction (MI). Acute changes in plasma PAI-1 after MI is a predictor of mortality. PAI-1 levels are elevated in the individuals with hypertension, insulin resistance, hypertriglyceridemia, obesity, and the constellation of risk-factors known as the metabolic syndrome. PAI-1 is synthesized in the liver, vascular endothelium, vascular smooth muscle, and visceral adipose tissue. A number of factors have been shown to regulate PAI-1, including metabolic factors such as insulin, glucose, triglycerides; inflammatory cytokines such as tumor necrosis factor-α, transforming growth factor-β, interleukin-1, and more notably, components of the RAAS, namely angiotensin II and aldosterone.