A virtual environment, which is created by computer graphics and an appropriate user interface, can be used in many application fields, such as teleopetution, telecommunication and real time simulation. Furthermore, if this environment could be shared by multiple users, there would be more potential applications. Discussed in this paper is a case study of building a prototype of a cooperative work environment using a virtual environment, where more than two people can solve problemscooperatively, including design strategies and implementirig issues. An environment where two operators can directly grasp, move or release stereoscopic computer graphics images by hand is implemented. The system is built by combining head position tracking stereoscopic displays, hand gesture input devices and graphics workstations. Our design goal is to utilize this type of interface for a future teleconferencing system. In order to provide good interactivity for users, we discuss potential bottlenecks and their solutions. The system allows two users to share a virtual environment and to organize 3-D objects cooperatively.