Molar Kerr constants and apparent dipole moments are recorded at 25° for acetonitrile, propionitrile, isobutyronitrile, t-butyl cyanide, chloroacetonitrile, trichloroacetonitrile, and benzonitrile, all in carbon tetrachloride, and for malononitrile in benzene. Inductive effects in these molecules are briefly discussed. Estimates of the anisotropic polarisability of the C-CN group in various environments are obtained. A regular increase of anisotropy is apparent for the C-CN group in the series MeCN, MeCH 2·CN, Me2CH·CN, Me3C·CN. The C-CN data from MeCN are satisfactorily applicable to Cl3C· CN, whilst, for ClCH2·CN, those from Me2CH· CN are most appropriate. The results for CH2(CN)2 anomalous, suggesting either bending of the C-CN group, exaltation effects, or solute-solvent interactions. The C-CN group polarisability in C 6H5·CN is much more anisotropic than in the aliphatic nitriles.