Serine protease inhibitors (Serpins) play an important role in regulating a wide array of diverse biological activities, representing up to 2-10% of circulating plasma proteins. The serpin suicide inhibitors regulate coagulation (thrombosis and thrombolysis), neurotrophic factors, hormone transport, complement and inflammation, angiogenesis, hormone transport, and blood pressure among many other biological reactions. Select serpins have been associated with progression or remission of selected cancers, making them valuable for therapeutic or diagnostic use. Plasminogen activator inhibitor-1 (PAI-1), the main regulator of thrombolysis, has the potential to either reduce or accelerate tumor growth but blockade of PAI-1 has recently been reported to reduce cancer cell migration, proliferation and survival through modulating the function of urokinase-type plasminogen activator receptor. Maspin is a non-inhibitory serpin, that increases cancer cell sensitivity to apoptosis and inhibits cancer cell migration thus providing a serpin that blocks tumor gorwth. Pigment epithelium derived factor (PEDF) has potent anti-angiogenesis activity and also promotes cancer cell apoptosis. Among other serpins, the mammalian serpin, neuroserpin, and the myxomavirus derived serpin, Serp-1 are under investigation in our lab for their potential tumor-suppressive functions. Further study on the efficacy and mechanisms of serpin mediated anti-cancer activity is warranted in order to develop new serpin-based approaches in cancer therapy.