This paper is a report upon some of the interrelated analytical and experimental studies designed to provide information on the combustion of boron particles in a high-speed air stream. The program upon which this work is based involved single particle ignition and combustion studies, B2O3 condensation studies, and axial and lateral injection of the effluent from a B-O-H-N gas generator into a supersonic air stream. This paper will emphasize the axial and lateral injection studies. Experimental data include profile measurements associated with both axial and lateral injection of hot and cold particle-laden primary streams injected into a variable temperature high-speed airstream. In addition, still color photographs and movies have been obtained. The analyses include treatments of coaxial mixing and combustion, and penetration for the description of the axial and lateral injection configurations, respectively. The coaxial analysis includes a special formulation for the turbulent diffusion of the particulate phase and the lateral injection analysis includes a treatment of the coupled gas-particle trajectories. Comparison of the analysis with the experiments shows very good agreement for both the coaxial and lateral injection flows provided the former is based upon the new mixing analysis and the latter employs a drag law based upon experiments with particulate clouds undergoing large accelerations.