High power supersonic plasma guns operating in excess of 200 kW can produce molten particles with 3 to 4 times the impact velocity of conventional plasma sprays. With this increased range of particle velocity it is important to understand the relationship between the torch input parameters and the sprayed particle velocity, temperature, pattern and size. Stainless steel particle velocity, temperature, size and relative number are measured for a high power plasma spray system operating at 110 kW. At the same torch operating conditions the plasma and particle flow fields are simulated with a newly developed computational model. It was found that the injection geometry plays an important role in the particle entrainment, heating and acceleration. In spite of the complexity of the system, i.e. supersonic plasma velocity with a high swirl component, the simulation produced reasonalble particle trajectories resulting in good agreement between the calculated and measured particle velocity, temperature and size distributions.