A comprehensive experimental investigation of the effects of hydrogen chloride concentration on the deposition rate and stoichiometry of SiC films produced through thermal decomposition of methyltrichlorosilane (MTS, CH 3 SiCl 3 ) is carried out in a gravimetric hot wall reactor of tubular geometry. The study is conducted under subambient pressures and in the temperature range 1173-1473 K. Deposition rate measurements are carried out with HCl added to the MTS/H 2 feed mixture to simulate the depletion of gas phase deposition precursors and the formation of HCl along the length of the reactor. The effects of HCl addition are studied at different locations in the CVD reactor for reactive mixture flow rates in the range 200-400 cm 3 / min, and 1:10 or 1:20 MTS/H 2 ratio. Very strong effects of HCl on the deposition process are suggested by the experimental results. It is also found that for certain values of the other operating parameters of the process, two stable deposition rates, differing by more than an order of magnitude, may be encountered at the same value of HCl concentration. A simple expression is formulated for the deposition rate of SiC in terms of the gas phase concentrations of MTS and HCl, and the temperature. This expression is employed in a simple plug-flow reactor model, and the predicted results are compared to the experimental measurements of deposition rate and HCl concentration levels needed to stop the deposition of SiC.