This paper investigates the influence of inter-particle collisions on the particle phase variables in the configuration of a free turbulent round jet laden with solids, i.e., considering the so-called four-way coupling. As a result, and due to the absence of walls confining the flow, the effects of particle-particle interactions start to be relevant for larger mass loading ratios when compared with confined flows, such as those occurring in pipes or channels. Interestingly, the particle phase fields are modified similarly to what happens in the previous confined flows: the profile of mean axial velocity flattens and the turbulence tends to be more isotropic when inter-particle collisions are taken into account. However, the associated mechanisms are slightly different. (c) 2006 Elsevier Ltd. All rights reserved.