Objective To introduce the clinical manifestations of REM sleep behavior disorder (RBD) which hasn't been reported in China ever before and to discuss the possible causes and mechanisms of the disease. Methods Ten cases of RBD verifted by polysomnography(PSG)were analyzed retrospectively. Results All patients were senile or in middle ages and most of them were male.The main clinical features included violent movements,shouting and other abnormal behaviors occuring in dreams when they fell asleep.Four cases were diagnosed as Parkinsonism,2 as multiple system atrophy and 1 as cerebral trauma.The causes of another 3 cases were unknown.all symptoms of them were relieved by using clonazepam administered prior to sleep.The PSG of all cases showed a loss of normal muscular atonia and an appearance of EMG activities during REM sleep. Conclusions RBD should be considered when patients showed abnormal especially violent behaviors in sleep.PSG should be essential for its correct diagnosis and the differentiation from partial complex epilepsy.Clonazepam given prior to sleep should be effective for treatment.