The electronic structure of conjugated polymers of current interest in the development of novel organic light-emitting diodes, poly(p-phenylenevinylene) and its derivatives, has been studied experimentally by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy and X-ray photoelectron spectroscopy as well as theoretically using quantum-chemical calculations. The pi-electronic structure near the Fermi level, which plays a major role in such phenomena as charge carrier injection, interface formation and light emission, has been the focus of our study on the pristine polymers. Also, the early stages of metal/polymer interface formation have been studied, namely aluminum and sodium on poly(2,5,2',5'-tetrahexyloxy-8,7'-dicyano-di-para-phenylenevinylene).