Chlorosilanes contaminated with boron-containing impurities can be purified by passing the chlorosilane vapor through a silica fixed bed. Normally the boron level in trichlorosilane is reduced by about 90-99+% by the use of this process. The capacities of the silica columns for the purification of trichlorosilane generally are in the range of 1500-2000 pounds trichlorosilane per pound of silica. The purified chlorosilane is particularly well suited for the production of polycrystalline silicon. Polycrystalline silicon containing 0. 03 ppba (parts per billion atomic) has been prepared from trichlorosilane purified with this process.