<b>FT IR and FT RAMAN SPECTRA of 4 Chloro 2 Methyl Benzonitrile</b> FT IR spectrum of 4 chloro 2 methyl benzonitrile in the region 400 4000 cm 1 has been recorded in KBr pellet technique with a Bruker IFS 66 Fourier transform spectrometer. FT Raman spectrum in powder form has been recorded in the region 50 4000 cm on a Bruker IFS 66 optical bench with an FRA 106 Raman module attachment interfaced to a microcomputer. Geometry and vibrational wavenumbers were calculated using ab initio calculations with HF method. The results were compared with experimental values. The observed FT IR and FT Raman vibrational frequencies were analyzed and assigned to different normal modes of the molecule. Most of the modes have wavenumbers in the expected range and the error obtained was, in general, very low. Using PEDs, the contributions were determined for different modes to each wave number. From the PED, it is apparent that the frequency corresponding to C=N stretching contains 88 contribution from the C=N stretching force constant and it mixes with C CN stretching mode to the extent of 12 . FT IR, RAMAN, SPECTRA, 4 chloro 2 methyl benzonitrile, spectrometer, PED 11-14 Issue-3 Volume-6 Virendra Kumar Sharma