A second-order closure technique for the compressible turbulent boundary layer equations has been developed. The technique is employed in the calculation of boundary layers with surface injection of similar and foreign gases. Theoretical results for M approximately 3 and several air injection rates provide favorable comparison with experimental data. Theoretical mean velocity and mass fraction profiles for a propane injected oxygen boundary layer are also presented. The additional ability of the technique to accommodate finite rate chemical reactions in a multi-species system was investigated. Preliminary results are provided for the rapidly developing region of flow downstream of an ignition and turbulence source. Application of the closure technique to the calculation of a variety of reacting shear flows is currently being performed at ARAP.