The general relation between one-electron electric properties e (dipole moment, polarizability, hyperpolarizability, etc.) of molecules calculated as energy derivatives (E) and as dipole expansion (D) is derived: epsilon(E) = epsilon(D) + epsilon(NHF), where epsilon(NHF) represents the non-Hellmann-Feynman correction, which vanishes for wave functions satisfying the Hellmann-Feynman theorem. It is shown that in cases when the wave function does not satisfy the Hellmann-Feynman theorem (e.g., limited CI) not only the NHF correction may be very large, but what is more important, the elements of static polarizability tensors (alpha, beta, gamma, etc.) obtained via the dipole expansion are non-physical because they do not satisfy the Kleinman symmetry, and for example alpha(ij)(D) not equal alpha(ji)(D), beta(ijj)(D) not equal beta(jji)(D) or gamma(ijji)(D) not equal gamma(jjii)(D) (for i not equal j, i = x, y, z). Finally, it is concluded that in the case of wave functions which do not satisfy the Hellmann-Feynman theorem only energy derivative methods are the correct way for calculations of one-electron electric properties of molecules. (C) 2002 Elsevier Science B.V. All rights reserved.