Tangential supersonic slot injection (M = 1.7) of air into a supersonic air stream (M = 2.91) was studied with a dual hot wire probe. This probe was used to simultaneously determine total temperature and mass flux. Mean profiles across the entire flow field at three axial stations (x/h = 4, 10, 20) were obtained, as well as the temperature and mass flux turbulence intensities. The probe can be used anywhere except at locations where features of the flow are smaller than the separation between the wires (0.18 mm). The calibration of the probe can be repeated with less than a three percent change in calculated Nusselt number. The hot wire probe can also be tuned to obtain a high frequency response. The interaction of a shock wave, caused by a wedge placed on the upper tunnel wall, with the mixing region was investigated. Little change in the mean profiles was observed, but there was a significant increase in turbulence levels.