In the presence of catalyst composed of n-butyl lithium and titanium tetrachloride in n-hexane solution in a nitrogen atmosphere the polymerization of phenylacetylene took place readily producing polyphenylacetylene in moderate yields．The polymers were partly soluble in benzene and the soluble fraction had an average molecular weight around 1100．The infrared spectra of the polymers showed that they probably have the linear conjugated polyene structure．Electrical measurements of the benzenesoluble fraction indicate a conductivity around 10-11 ohm-1·cm-1 at room temperature and a resistance-temperature relationship which is typical of semiconductors．Magnetic measurements of the same fraction show a paramagnetism of 0.2×10-6 cgs unit．