Control of the orientation, diameter, and length of silicon nanowires (SiNWs) is achieved in large-scale single-crystalline SiNW arrays fabricated by a statistical electroless metal deposition technique. Taguchi methods are employed to optimize the diameter control and to understand the influence of all processing factors on the growth. The < 100 > directions are found to be the preferred crystallographic orientation of the growing SiNWs (see figure).