[en] The rotational diffusion equation for a dipole in the presence of an oscillating field is solved by expansion of the orientational distribution function in terms of Legendre polynomials and harmonics. The nonlinear response of the average dipole moment is studied as a function of field strength and frequency. Outside the linear regime the in-phase and out-of-phase response as functions of frequency do not satisfy Kramers-Kronig relations. A comparison is made with the nonlinear response calculated from approximate macroscopic relaxation equations proposed by Shliomis and by Martsenyuk et al. The response of a macroscopic system of interacting dipoles is calculated in the mean-field approximation for a spherical sample