We present an ab initio study of surface energies, surface magnetism and work functions of the 3d transition metals. The calculations are performed by means of a spin-polarized Green's function technique based on the tight-binding linear muffin-tin orbitals method within the atomic sphere approximation. In addition to the conventional paramagnetic and spin-polarized calculations we use the fixed spin-moment method to clarify the effect of magnetism on the surface energies. The results are shown to be consistent with a Friedel model of d-electron bonding combined with spin-split state densities as well as with a Stoner-type description. It is established that the anomaly in the surface energy of the 3d metals deduced from surface tension measurements is purely a magnetic solid state effect. In addition, it is found that magnetism reduces the surface energy of open surfaces, e.g. the (001) crystal faces, to the extent that the usual anisotropy of the surface energy is reversed. Thus a complete realization of the surface energy anomaly only takes place in the less close-packed surface facets.