The anisotropic magnetoresistance effect of alloy films and so-called giant magnetoresistance of superlattice multilayer films are reviewed. The usefulness for phenomenological explanation of both the anisotropic magnetoresistance and giant magnetoresistance of the two-current model, suggested first by Motto and subsequently extended by several researchers, is stressed. The relationship between the magnetoresistance and the magnetic anisotropy field is demonstrated for films exhibiting either anisotropic magnetoresistance or giant magnetoresistance. The magnetoresistances of multilayer films both with and without magnetic interaction between adjacent layers are compared. The dependence of the magnetoresistance on temperature is briefly discussed.