The transmission matrix approach is used to evaluate perpendicular magnetotransport in metallic multilayers that consist of two magnetic slabs separated by a non-magnetic spacer. We employ the spin-polarized surface Green function technique within the framework of the tight-binding linear muffin-tin orbital method. Our approach allows both the ballistic and the diffusive regime of magnetotransport to be treated on equal footing. The effect of disorder is included in terms of lateral supercells confined to individual atomic layers. In this paper, we apply the method to fcc-based Co/Cu/Co(001) trilayers. © 2000 Elsevier Science B.V. All rights reserved.