The electric dipole moments (μ), first (β) and second (γ) hyperpolarizabilities of a series of Schiff bases with different donor-acceptor substituents and regulating groups (R) were calculated using ab initio quantum mechanical methods. The hyperpolarizabilities obtained have been found to be rather adequate for assessing connectivities between the electronegativities of substituents and regulating groups and non-linear optical properties. © 2004 Elsevier B.V. All rights reserved.