The magnetic properties of idealized bcc Fe/Cu and Fe/Cr superlattices have been investigated by carrying out self-consistent spin-polarized linearized muffin-tin orbital/atomic sphere approximation and linearized augmented spherical wave methods/atomic sphere approximation calculations. Structures composed of 2-4 Fe, 2-11 Cu, and 2-6 Cr monolayers were considered. In Fe/Cu, the exchange coupling between successive Fe slabs does not exhibit the FM to AFM crossover observed experimentally at about 9 Cu monolayers. In Fe/Cr superlattices having atomically abrupt interfaces, the exchange coupling exhibits short-range oscillations. When interfacial roughness is taken into account, these oscillations are smoothed. However, the averaged exchange coupling does not switch from FM to AFM at about 4-5 Cr monolayers as observed. Since experimental samples differ markedly from the idealized models employed, it is likely that structural and chemical imperfections will have to be taken into account in order to reconcile first-principles theory with experiment. In this context the structural distortion from bcc to bct in Fe/Cu, and interfacial roughness and localized Fe impurities in Fe/Cr and discussed.