Linear polymer of acetylene was prepared in which the oxygen content was as low as 0.7 %. The electrical conductivity and Seebeck voltage but not the energy gap depended on the extent of oxidation of the samples. Adsorbed donor and acceptor gases affected electrical conductivity but not e.s.r. spin assay. It was concluded that the degree of crystallinity in these polymers is of equal importance with chemical purity to achieve high electrical conductivity.