Obesity is a common disorder and a known risk factor for thrombotic complications. Development of obesity is associated with extensive modifications in adipose tissue involving adipogenesis, angiogenesis and extracellular matrix proteolysis. The fibrinolytic (plasminogen/plasmin) system plays an important role in these processes. Studies using a nutritionally induced obesity model in transgenic mice support a role of the fibrinolytic system in adipogenesis and obesity. Studies using venous or arterial thrombosis models in obese mice, with impaired fibrinolytic activity, confirm a prothrombotic risk associated with obesity.