Purpose: This study aimed to determine whether patients with long-standing nocturnal bruxing behavior present different body movement activity during sleep compared with healthy subjects. Materials and Methods: Eleven bruxers and 8 nonbruxers were studied in the sleep laboratory, and motor activity was detected with sensor pads placed under the mattress. Movements simultaneously recorded on videotapes were classified according to their duration and grouped in different types according to their characteristics. Results: Subjects with bruxism had significantly more movements during sleep compared with controls; the difference was especially obvious for movements of short duration ( 5 seconds). The differences became significant from the fourth hour of sleep. These short movements were twitches, jerks, or any sudden, brusque movements of the extremities, but without the periodicity encountered in, for example, periodic limb movements during sleep. No significant relationship was found between the occurrence of masseter activity and movements. Conclusion: The findings suggest that subjects with nocturnal bruxism have movement disorders that are expressed not only as grinding or clenching of the teeth, but also as an increase of short-duration body movements during sleep. This reinforces the hypothesis of a central etiology common to both bruxism and short movements during sleep.