Raman and IR spectra of phenylacetylene dissolved in methylcyclohexane and acetonitrile have been recorded, The IR line widths and Raman Isotropic line widths of totally symmetric A(1) vibrations of phenylacetylene-the stretching mode of the ethynyl group C=C (v(S)(C=C)), the phenyl ring in-plane stretching (v(8a)), the C-phenyl group stretching (v(S)(C-Ph)), and the phenyl ring breathing (mixed with trigonal vibration) (v(12))-have been recorded, The spectra have been measured as a function of concentration at room temperature. Theoretical models of vibrational dephasing have been tested and compared with experiment.