Stimulated by recent experimental evidence for the formation of ultrathin close-packed films of vanadium ͑V͒ and also indication of ferromagnetic order in epitaxial V / Ru multilayers, we have performed firstprinciples electronic structure and total energy calculations to study the stability and magnetism of the metastable hcp and fcc structures of V and also the effects of the surface and interface on these properties. The systems include ultrathin films of a few monolayers of V grown on hcp ͑0001͒ ruthenium ͑Ru͒ substrates and V / Ru superlattices as well as bulk bcc, fcc, and hcp structures. Our investigations are based on densityfunctional theory with local density approximation plus generalized gradient corrections. Both the frozen-core projector augmented-wave approach and the all-electron full-potential linearized augmented-plane-wave method are utilized. First, our calculations show that all three bulk structures are nonmagnetic at their respective minimal energy lattice constants. However, all the three structures transit first to a low-spin ferromagnetic phase and then to a high-spin phase as the lattices expand. Second, we find that thin films on hcp ͑0001͒ Ru with one monolayer of V in either hcp or fcc stacking sequence have a magnetic moment of the order of 1 B . A thin film of three monolayers of V in fcc stacking sequence is weakly ferromagnetic, though the other thin films with more than one monolayer of V are essentially nonmagnetic. A free-standing film of three V monolayers in hcp stacking sequence is also ferromagnetic with sizable magnetic moments. We also find that the V 2 ͑hcp͒ /Ru 6 ͑hcp͒ and V 3 ͑hcp͒ /Ru 5 ͑hcp͒ superlattices exhibit ferromagnetism with a small total magnetic moment of a few tenths of B . Lattice relaxation has the trend of decreasing the magnitude of the magnetic moments. All the other V n /Ru m ͑hcp͒ superlattices ͑n =1,4,5 and m =5,6 as well as n = 3 with fcc or bcc stacking sequence͒ are essentially nonmagnetic. Finally, our calculations show that the stacking sequence has significant effects on the formation of stable atomic magnetic moments of V and is also important for the energetic stability of these systems.