The Raman spectra of the solid, nematic, and isotropic liquid phases of 4-cyano-4′-pentyl-biphenyl (5CB) and 4-cyano-4′-pentyl-d11-biphenyl (5CB-d11) are reported together with the method of synthesis of 5CB-d11. A comparison of the spectra of the isotropic liquid phases of 5CB and 5CB-d11has led to a partial assignment of these spectra. For each compound, the spectra of the fluid phases resembled each other, but differed from the corresponding spectrum of the solid phase. In particular, the cyano streching vibration occured as a doublet in the spectra of the solid phases of 5CB and 5CB-d11, but as a single band in spectra of the fluid phases. The nematic to isotropic liquid transition temperature of 5CB-d11was 1[ddot] lower than that of 5CB.