The research program of Unit 1.2A, Therapeutic Vascular Systems, of the National Science Foundation/Engineering Research Center (NSF/ERC) is described. The unit's goal is to develop polymeric stents (stiffening elements) that can be implanted in a diseased artery simultaneously or sequentially to percutaneous transluminal coronary angioplasty (PTCA), and to make these stents in such a way that they will become encapsulated by tissue, degraded, and eventually absorbed. The unit produced stents from nylon, polyglycolic acid, and poly(L-lactic acid) and developed a method for in vitro evaluation of mechanical properties. A poly(L-lactic acid) stent has been placed in the femoral artery of a dog, and the vessel has remained patent for several months. In vitro testing of Vicryl (lactic/glycolic acid copolymer) stents show that they rapidly lose modulus due to plasticization by warm water, and nylon was also unsatisfactory, although better than Vicryl.