The rehabilitation robot LOKOMAT has been developed at the Balgrist University Hospital to automate treadmill training of spinal cord injury and stroke patients. A virtual environment setup was implemented to increase patient's motivation and provide biofeedback, consisting of visual, acoustic and haptic modalities. Based on the knee and hip angles of the orthosis, an animated figurine moves through a virtual environment. This contribution describes the setup of the system and selected technical performance parameters. We focused on delay times caused by the setup, stability of the haptic obstacle rendering and on the level of immersion as judged by four healthy subjects. Results show that subjects judged the system's performance well (questionnaire scores over 80%). Problems exist though for obstacle rendering (questionnaire scores of 55%).