This paper deals with the evolution of a gas-solid interface during growth of amorphous CVD films. The aim of the analysis is to show that a comprehensive gas-solid CVD model may simplify significantly under conditions of two limiting cases: kinetic and diffusion-limited growth. The linear stability behavior of the simplified model was found to be almost identical to that of the original and more comprehensive model. It was found that planar film growth was inherently stable under kinetically controlled deposition conditions, but under diffusion-limited conditions, planar film stability depended on the magnitude of the dimensionless group 9Pe, which represents a Damkdhler number of deposition. Numerical solution of the simplified model showed that an increase in 9pe adversely affected the uniformity of film deposition. Predicted morphological phenomena were found to be very similar to experimental observations (Viljoen,et al,1994).