A simple, unified, one-dimensional model has been developed to relate the effects of plasma spray parameters on the temperature and velocity of the plasma and particles and on the void content in the coating. The torch, spray, and substrate regions in a plasma spray process were first modeled independently and then coupled so that the plasma and particle characteristics calculated in one region served as inputs for the subsequent region. Comparison of the model predictions with experimental data showed reasonable agreement. Deviations from the measured data were attributable to the simplifying assumptions used in modeling the different regions of the process. A parametric analysis of the unified one- dimensional model showed that, despite its simplicity, the model is well suited for optimizing process parameters in terms of particle type and size to obtain high- integrity coatings.