The magnetostriction, parallel and perpendicular to the applied magnetic field, has been measured for the RENi 2 intermetallic compounds (RE = Pr, Nd, Sm, Tb, Dy, Ho, Er and Tm), between 3.8 K and well above the Curie temperatures in polycrystalline samples. From the comparison with a theoretical analysis, the temperature dependence for the phenomenological magnetostriction parameters h 1 and h 2 has been extracted for the compounds SmNi 2 and NdNi 2, in good agreement with the Callen and Callen Î frbuilt:5/2[ L −1( m)] law. An analysis within the crystal field (CEF) theory has allowed the determination of the single-ion magnetoelastic coupling parameters M ϵ 2 (for the tetragonal-distortion mode) and M ϵ 2 (for the rhombohedral mode) for the compounds TbNi 2, DyNi 2, HoNi 2 and ErNi 2 at the ordered regime. A relevant result is that the point charge model for the distorted CEF is reasonably well accomplished. Parastriction calculations in PrNi 2, TbNi 2 and DyNi 2 seem to indicate the weakness of quadrupolar pair interactions.