The Raman and infrared spectra of the 7-cis, 9-cis,ll-cis, 9-cis,l3-cis and ll-cis,l3-cis isomers of retinal have been recorded for the first time. The spectra of the all-trans, 9-cis, 11-cis and 13-cis isomers were also recorded for comparison. The isomers were isolated from a photoisomerization mixture of the all-trans isomer and their configurations were identified by means of 'H NMR or Raman spectroscopy. The Raman spectra of the isomers in CCI, solution were recorded using a flow method, the 457.9 nm line of an Ar+ laser and a Raman spectrometer equipped with a multichannel detector; their infrared spectra were recorded by using an FT-IR spectrophotometer. Comparison of the Raman spectra of the mono-cis isomers revealed key bands which discriminate between unmethylated-cis ( 7 4 s and 11-cis) and methylated-cis ( 9 4 s and 134s) configurations. The key bands were related to local vibrations around the particular cis double bond. Unmethylated-cis configurations show (1) a unique band around 1280-1270cm-' due to a coupled mode of A, type (with reference to the local symmetry C,, of the cis-C-CH=CH-C group) consisting of the two C-H in-plane bendings and the C=C stretching, (2) a stronger band at 969 cm-' ascribable to an A,-type coupled mode consisting of the two C-H out-of-plane waggings and the C=C torsion and (3) a unique band at 563 cm-', tentatively related to an A,-type coupled mode consisting of the C-C=C and C=C-C deformations. Methylated-cis configurations show a stronger Raman band around 880 cm-' due to C-Me stretchings. Raman bands characteristic of each cis configuration (Fcis, 9-cis, 11-cis or I f c i s ) also are discussed.