The polymerization of acetylene and its derivatives is one of the fundamental methods for the synthesis of linear conjugated polymers, which are beginning to be used at the present time as organic semiconductors. The simplest of the conjugated polymers, polyacetylene, has been synthesized with a wide variety of catalysts. In this paper the authors deal with the polymerization of 2-ethynylthiophene (2-ET) by WCl//6- and MoCl//5-based catalysts. The characterization and physical properties of the resulting polymer are also discussed.