There are several types of biofeedback. The most common kind measures muscle tension and the amount of electrical activity in the muscle is displayed either visually or aurally in a way that allows patients to learn to relax their muscles. Another form uses the amount of moisture on the skin surface as the feedback source. Two newer technologies allow for the feedback source to be cardiac activity and brainwave (alpha) activity to be monitored. There have been several quality studies that show a benefit for muscle biofeedback, particularly in tension headache. The other modalities are being used with good effect in selected patients but there are no definitive studies comparing this approach with pharmacologic or other approaches. Certainly from an intuitive viewpoint, it makes sense that biofeedback would benefit certain headache sufferers.