We present a computer vision and virtual reality application for cancer patients. Currently, visualization and imagery techniques are becoming a routine part of the treatment of the ill. Mounting evidence shows the effectiveness of using self-imagery to encourage the immune system to boost its effort to defend the body from disease. Furthermore, while stress has been shown to retard the immune system, relaxation has the opposite effect. To that end, we are developing a virtual reality visualization tool for cancer patients called Staying Alive. The system provides a means for users to relax while directly visualizing their immune systems fighting off their diseases. White, red, and malignant blood cells are modeled as simple autonomous agents in the environment. The user controls a white blood cell, navigates through the blood stream, and "digests" malignant cells found along the way. To control the virtual environment, the user, free of wires and other such encumberments, engages the system simply by standing in a room, practicing T'ai Chi gestures. Computer vision techniques are employed to recognize the gestures in real time.