Plasminogen activator inhibitor type-1 (PAI-1), is a unique member of serpin superfamily, the primary regulator of plasminogen activation and therefore essential factor regulating physiological thrombotic/fibrinolytic balance in vivo. Via interactions with integrins and extracellular matrix components it orchestrates also cell adhesion and migration. Therefore, PAI-1 is considered one of the key regulators of tumor invasion and metastasis, as well as cancer-related angiogenesis. This review summarizes recent findings on the structure and functional activity of the plasminogen activator inhibitor type-1, and current opinions on its role in tumorigenesis.