Abstract Electronic polarizabilities and sizes of ions in A N B 10−N type semiconductors (PbS, PbSe, PbTe and SnTe) have been deduced in the present study. The free ion polarizabilities of Sn 2+ and Pb 2+ ions are estimated approximately following the procedure of Pauling. The effect of crystalline potential is then estimated on free cation polarizabilities. An empirical relation between ionic radii and polarizabilities has been applied to deduce the ionic sizes and anion polarizabilities. The calculated molecular electronic polarizabilities agree well with the experimental values. The variation of dielectric constant with strain has also been estimated in each crystal and the results are explained in terms of the optical anisotropy parameter.