A number of high-velocity oxygen-fuel flame (HVOF) systems have evolved during the last 9 years. The most advanced is now challenging the coating qualities produced by the very successful detonation (D-Gun) process. The fundamentals of these various processes are described and compared. A mathematical analysis of an established HVOF gun is profiled. Gas and particle temperatures, velocities, pressures, and Mach numbers are calculated and plotted at various points within the gun and spray stream. Significantly, all measured values were in close agreement with calculated and predicted values. Flow patterns and shock-wave phenomena are also described and compared with actual observations.