Depolarization ratios and gas phase Raman scattering differential cross sections of all Raman active fundamental vibrations of C2H2, C2HD and C2D2 are reported in absolute units. These quantities may be easily interpreted in terms of bond polarizability parameters. The anisotropy of the molecular polarizability of C2H2 determined from the bond polarizability parameters is consistent with values reported by previous authors. The derivative of the CH bond polarizability tensor with respect to the stretching of the CH bond is shown to have the same value in acetylene as in methane, within experimental accuracy. © 1982 Taylor & Francis Ltd. Peer reviewed