Two cases of juvenile myoclonic epilepsy (JME) presented with myoclonic jerks and EEG activation after eye closure, without sensitivity to intermittent photic stimulation. The effect of eye closure was computed by comparing discharge rates of polyspike-and-wave (PSW) complexes after eye closure and after eye opening. For one patient, never treated pharmacologically, a nocturnal polysomnograph was performed to study the variation of discharge rates of PSW complexes during wakefulness and sleep. The rate of PSW complexes was high during wakefulness before sleep onset, increased during spontaneous nocturnal awakenings, and became maximal during final morning awakening. Among nonrapid eye movement (NREM) sleep stages, EEG epileptiform activity was maximal during stages III and IV. Discharges were completely suppressed by rapid eye movement (REM) sleep. Awakenings following deep NREM sleep were very activating if no REM sleep was interposed. Awakenings from light NREM sleep were much less activating. There were no EEG abnormalities in awakenings immediately following REM sleep. Results suggest that REM sleep, similarly to eye opening, plays a role in inhibiting EEG manifestations of JME with eye closure sensitivity.