Methylchlorosilanes were successfully chlorinated with sulfuryl chloride, when azo-bis-isobuty-zonitrile was used as free radical initiator, givinb the corresponding monochlorinated products. The rate of reaction decreased when more Si-Cl bonds were present in the silane to be chlorinated. Increasing the quantity of the initiator increased the rate of reaction. Trimethylchloromethylsilane was also chlorinated with sulfuryl chloride and benzoyl peroxide, both dichloromethyltrimethylsilane and di(chloromethyl)dimethylsilane were simultaneously obtained.