Silicon nanowires can be grown by chemical vapor deposition. Using a SiH4:HCl:H-2 gas ratio of 3:1:96, a pressure of 1333 Pa, a substrate temperature of 1223 K and radiant heating by a halogen lamp, an appreciable quantity of silicon nanowires formed on Si, SiO2 and Si3N4 substrates while on a Mo substrate, a silicon film deposited. An increase in the pressure to 13332 Pa led to a deterioration in nanowire growth. Using a hot filament at 3073 K suppressed nanowire growth but resulted in deposition of a normal silicon film. The highly anisotropic growth of silicon nanowires was attributed to highly anisotropic landing of charged silicon clusters.