Germanium nanowires with diameters from 10 to 70 nm and lengths up to 3 pm have been grown by Vapour-Liquid-Solid Molecular Beam Epitaxy (VLS MBE) on Ge (1 1 1), Si (0 0 1) and Si (1 1 0) substrates. The growth of nanowires was induced by gold droplets. We show that substrate temperature and germanium deposition rate, which determine surface diffusion length, are key parameters governing nanowires nucleation and growth phenomena. We also show that nanowires growth directions are independent of the strain induced by lattice mismatch. (C) 2010 Elsevier B.V. All rights reserved.