The electronic structure of threeand five-plane films of ferromagnetic Ni{100) has been computed self-consistently, with the use of an atomic-orbital basis. A surface-state band obtained for the five-plane film corresponds to surface-sensitive bands observed recently in angle-resolved photoemission measurements. 80th films have 8 work function of 5.0 cV Rnd Rn cnhanccd surface IQRg-nctlzat1on (ESM) compared with that of thc 1nncr plRQcs, wh1ch have csscntlally thc bulk IQagnct1-z8tlon. The contllbut1ons of dchybIldlzRtlon Rnd band narrow1ng to ESM Rrc Rsscsscd by I'cpcatlQg the calculations with sp-d matrix elements omitted. Also, while the occupancy of the nominal d bands decreases at the surface, their d character increases; cancellation of these effects explains why the d-orbital occupation number is nearly independent of the coordination. On the other hand, a definite surface charge transfer from p Io s orbitals is observed in the calculations. We also studied Ni(100) monolayeIs with lattice spacings 10% smalleI, and 20% larger, than the bulk spacing. In these systems also, the magnetization increases as the atomic limit is approached, while the number of d electrons is nearly constant.