Reports have appeared recently describing the successful reduction of nocturnal bruxism through nocturnal biofeedback. These claims of effective treatments rest mainly on the use of a single index of integrated masseter EMG levels as a measure of bruxism and are based only on short-term effects. The present study was conducted to provide a more rigorous evaluation of the effectiveness of nocturnal biofeedback for nocturnal bruxism through the use of all-night polysomnographic recordings. The results from multiple indices of bruxism are internally consistent and indicate that simple nocturnal biofeedback does not appear to be effective in reducing nocturnal bruxing. Recommendations are made for a more comprehensive approach to the treatment of nocturnal bruxism.