The major components of the fibrinolytic system are responsive to hormones, growth factors and cytokines in a wide variety of primary and neoplastic cell lines. These effectors commonly cause increased biosynthesis of PAI-1 with overall suppression of fibrinolysis. Recent studies have indicated that certain agonists, in particular the inflammatory cytokines, may suppress fibrinolysis in animal models. These findings provide a correlate to the clinical observations which relate an increase in PAI-1 levels with thrombotic risk. On the other hand, induction of t-PA and u-PA biosynthesis by growth factors has been related to tissue remodelling and cell migration associated with angiogenesis and tumour metastasis.