The usefulness of Mössbauer spectroscopy for studies of magnetic multilayer systems is discussed. By applying 57Fe Mössbauer spectroscopy, the behavior of ultra-thin magnetic layers is studied. Position-specified information is available by preparing samples in which 57Fe probes are located as desired, to provide depth selectivity. For the studies on non-magnetic layers, hyperfine field observations by 197Au and 119Sn probes are worthwhile. Spin polarizations in Au layers penetrating from neighboring ferromagnetic 3d layers are estimated from Au Mössbauer spectra. Spin polarizations in Au layers are also studied by inserted Sn probes in Au/3d multilayers. In Sn spectra for Cr/Sn multilayers, it is found that remarkably large spin polarization penetrates into the Sn layers from a contacting Cr layer, which suggests that Cr atoms in the surface layer have a ferromagnetic spin alignment.