Perlecan is a large heparan sulfate proteoglycan (HSPG), which is a major component of the vessel wall. In relation to vascular biology, perlecan has been shown to be a potent inhibitor of smooth muscle cell (SMC) activity. In vivo experiments in animal models of arterial injury have shown that perlecan may inhibit thrombosis and intimal hyperplasia. On the other hand, perlecan has been shown to have opposing effects on endothelial cells (ECs), where it promotes in vitro and in vivo angiogenesis and plays an important role in mediating tumor growth. These diverse biological effects, or "the perlecan paradox", are discussed in this review paper. The properties of perlecan including inhibition of SMC activity and thrombosis while enhancing EC proliferation are ideal for the prevention of in-stent restenosis. Perlecan's pro-angiogenic effects may be used for the treatment of various ischemic diseases such as intractable coronary artery disease and peripheral vascular disease.