A computer simulation model for estimation of the interaction fields in fine particle systems has been developed. The method uses the experimental 8Mα(H) plot, constructed from the Fourier description of the initial magnetization curve and the hysteresis loop, and the 8M(H) plot, obtained from the remanence curves. The dependencies of the interaction fields on the external magnetic field have been obtained from the experimental data for a sample of a Ba–ferrite fine powder.