This paper describes a numerical model for the nucleation, growth, and transport of gas-phase particles formed during the chemical vapor deposition (CVD) of epitaxial silicon from silane. These particles can lower the deposition rate by consuming precursor, and contaminate the growing film via diffusion to the surface. This model has been constructed for use with the Sandia SPIN code, which contains a solver for the reacting flow and heat transfer in a vertical, rotating disk CVD reactor. A detailed gas-phase chemical kinetic mechanism for the thermal decomposition of silane was developed to simulate formation of small silicon clusters and the depletion of reactive intermediates through condensation. The particle model uses a moment transport formulation to examine the effects of total reactor pressure, temperature, rotation rate, inlet gas composition, and rate of particle growth via condensation on the characteristics of the particle population. Numerical results are presented in terms of the integral moments of the particle distribution which correspond physically to the particle number concentration, average particle diameter, and particle light scattering intensity. In situ validation experiments have been performed in an optically accessible reactor under conditions typical of silicon CVD. The rate of particle growth via condensation, controlled numerically by a global condensation parameter (GCP), was found to control the characteristics of the particle population. The numerical results were found to compare favorably with experiment if this GCP was properly chosen. (C) 2003 The Electrochemical Society.