In this work, we propose a numerical study of an axisymmetric turbulent jet discharging into co-flowing stream with different velocities ratios ranging between 0 and infinity. The standard k-epsilon model and the RSM model were applied in this study. The numerical resolution of the governing equations was carried out using two computed codes: the first is a personal code and the second is a commercial CFD code FLUENT 6.2. These two codes are based on a finite volume method. The present predictions are compared with the experimental data. The results show that the two turbulence models are valid to predict the average and turbulent flow sizes. Also, the effect of the velocities ratios on the flow structure was examined. For R-u > 1, it is noted the appearance of the fall velocity zone due to the presence of a trough low pressure. This fall velocity becomes increasingly intense according to R-u and changes into a recirculation zone for R-u >= 4.5. This zone is larger and approaches more the nozzle injection when R-u increases. (C) 2010 Elsevier Ltd. All rights reserved.