Electroencephalographic activity related to palatal myoclonus in REM sleep. Polysomnography, including electroencephalography, electromyography and electro-oculography was performed in three patients with palatal myoclonus (PM). The amplitude of the myoclonus decreased during sleep. The frequency did not change during non-REM sleep, but increased during REM sleep in two patients. Ocular myoclonus synchronized with PM disappeared during deep sleep stages in two patients and reappeared during REM sleep in one of them. In the other patient, ocular myoclonus was noted only in REM sleep, being absent even when the patient was awake. All patients showed episodic EEG activities synchronous with myoclonic jerks only in REM sleep. These episodes were noted 5-15 times throughout the night, and each episode lasting for 1-7 s. They were negative or positive waves of saw-tooth appearance which were distributed predominantly in the central region. During the episodes, the frequency of myoclonic jerks increased in two patients. Although it is known that REM sleep influences PM and ocular myoclonus, this is the first report demonstrating the electroencephalographic activity associated with PM. 