We present a computer vision and virtual reality application for cancer patients. Currently, visualization and imagery techniques are becoming an accepted adjunct in the treatment of cancer. 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 and red blood cells and malignant cells populate the virtual environment. The user navigates a white blood cell 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 sitting in a room, practicing T'ai Chi gestures. Computer vision techniques are employed to track the user's head and hands in 3-D and a Hidden Markov Model framework is used to recognize the gestures in real time..