The aim of this study was to investigate the effects on gait induced by a completely immersive Virtual Reality (VR) with and without perturbation. Ten healthy subjects were analyzed during over-ground walking in different conditions: standard gait, VR gait and perturbed VR gait. Results showed that subjects immersed in the virtual environment walked slowly, with decreased cadence (-13%) and stride length (-28%) as well as increased base of support in terms of step width (+20%). The perturbation of the VR caused an interesting effect: many computed parameters, still away from the standard gait condition, improved if compared to the unperturbed VR condition. In conclusion, walking in VR leads to gait instability, which is less pronounced in presence of perturbation, probably due to the reweight of sensory inputs. This study could represent the first step for the application of the proposed VR environment to pathological subjects.