The angular dependence of the magnetic properties of all known octahedrally coordinated oxo-bridged dimers with trivalent 3d transition metals are interpreted in terms of the most simple concepts. These concepts are based on a combination of kinetic exchange and the chemically intuitive angular overlap model. The use of an angular overlap model allows the separation of the sigma donor properties of the bridging oxide ligand into s sigma and p sigma contributions. An estimate of the s sigma and the p sigma angular overlap model parameters is given. An analysis of the magnetic properties of the known oxo-bridged dimers allows us to predict the magnetic properties of unknown oxo-bridged dimers with trivalent 3d transition metal ions.