The exact dispersion equation of electromagnetic modes propagating in structures that include tangentially magnetized ferrite film with surfaces bordered on media with different permittivity is derived. In the lowwavenumber range the comparison of the theoretical calculation with the experimental measurement of dispersion of magnetostatic surface waves propagating in the layered structures of such types as dielectrictangentially magnetized ferrite film of yttrium iron garnet–gadolinium gallium garnet is made.