Heterogeneous nucleation is governed by the interplay of interfacial energies between a substrate, a solid and a liquid. Although the intensity of these energies can strongly change with the orientation of the nucleus for anisotropic media, this parameter is not taken into account in the available nucleation theories. In this paper, the Gibbs free energy barrier for nucleation is computed for an arbitrary solid liquid interface energy. It is shown that anisotropy favors particular orientations of the nucleus on the substrate. Experimental evidence from the zinc aluminum system is given as an application of this extended nucleation theory. It also sheds new light on the texture of galvanized steel sheets. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.