Highly symmetric self-organized arrays of germanium nanowires with average diameters of ∼12 ± 3 nm were produced by chemical vapor deposition. The nanowires grew epitaxially on the faces of single-crystal Ge microcrystals produced in the same synthesis. The epitaxial growth occurred on several crystal faces with the resultant nanowire structure varying accordingly. The (111) growth direction was found to dominate, however. High-resolution TEM images of a system consisting of the NW and the substrate on which it grew epitaxially are also reported, specifically showing the interface between the two regions, thereby elucidating the growth mechanism.