Bruxism, the phenomenon of non-functional grinding of the teeth has been ascribed to various causes. Twenty patients with coma from different causes who displayed bruxism were studied with an attempt to correlate the phenomenon to the level of consciousness, eye movements, respiration, cold caloric test, motor deficits and sleep wake cycles. Bruxism was seen to appear at different levels of consciousness, but to disappear only after a significant improvement in the level of consciousness. A relationship with the appearance of sleep wake cycles was also seen.