Deposition of silicon from chlorosilanes is studied. Based on a model for gas-phase reactions involving SiCl3, SiHCl3, SiCl2, and HCl, the reaction constants for relevant gas-phase reactions are determined. Deposition is analyzed in two ways : one (effusive flux model) using the surface reaction probabilities of surf ace reactions, and the other (surface reaction model) derived previously by Korec in terms of surface reactions of SiCl2. Advantages as well as disadvantages of the two models are discussed by comparing fully numerical results with the experimental results available.