Plasminogen activator inhibitor type 1 plays a prominent part in the regulation of extra and intra-vascular fibrinolysis through the inhibition of plasmin formation. In addition to its role in the resolution of blood clots, PAI-1 is involved in a variety of other biological processes including extracellular remodeling, cellular mobility, embryo implantation, development and tumoral proliferation. Moreover, PAI-1 is also implicated in various pathological processes such as thromboembolic diseases, atherosclerosis and fibrosis formation, particularly in the kidney and the lung. Inhibition of PAI-1 activity or of PAI-1 synthesis by specific antibodies, peptidic antagonists, antisens oligonucleotides or decoy oligonucleotides has been obtained in vitro but need to be evaluated in vivo. All these findings may have new therapeutical implications, explaining the importance of studies on PAI-1 production and regulation.