This paper presents a virtual reality (VR)-hased computer-aided design (CAD) system for conceptual design by applying VR interfaces and geometric modelling techniques to improve the human computer interaction. The research has studied the human factors for designing an intuitive computer-aided design system. The results and experiences have led to a deeper understanding of the limitation of current CAD tools that are used for conceptual design and the requirements for the VR-based CAD system so the design activities that define the user interfaces of VR-based CAD system can be determined. The system uses a CyberGlove, developed by Virtual Technology Inc., as an input device so that conceptual designers are allowed full freedom to use different kinds of gestures to conduct various geometric shape operations instead of depending solely on keyboard and two-dimensional mouse. The implemented shape modelling techniques offered by the system include destruction, construction, and novel techniques for freeform feature creation and modification. The system operates on the Windows NT platform and hence inherits a number of Windows operating styles. It provides a friendly human-computer interactive mechanism, especially for those users who are familiar with the Windows operating system. The VR-based user interfaces are superior and better match the human sensory capabilities than those that are dependent on conventional keyboard and mouse input devices.