A systematic study of the gas-mixing pattern in an induction plasma reactor under atmospheric and low pressure conditions is reported. Different reactor configurations were investigated in which nitrogen is injected as an auxiliary gas either axially into an Ar/H-2 discharge in the center of the induction coil region, or radially through multiple orifices, into the plasma jet at the exit nozzle of the torch. Concentration mapping in the mixing zone was carried out. using a VG-Micromass-PC 300 D mass spectrometer at plasma power levels and reactor pressures, in the range of 13-24 k W and 35-93 kPa, respectively. Comparison of these results with cold-flow measurements underlined the substantial difference in the mixing pattern in each of these two cases. A considerably faster mixing of the gases is noted under cold flow conditions compared to that in the presence of the discharge. The results are discussed from the viewpoint of their use for optimum reactor design applied to the vapor-phase synthesis of ultrafine ceramic powders, using induction plasma technology.