Rapid differentiation of endothelial progenitor cells (EPCs) into confluent mature endothelial cells (see figure) is important in tissue engineering for the design of autologous, nonthrombotic, vascular grafts. A new method based on EPC culture on poly(sodium-4styrene-sulfonate)/poly(allylamine hydrochloride), that is, polyelectrolyte-multilayer-coated substrates, reduces the time from two months to two weeks.