Abstract OBJECTIVE: To evaluate the effect of epilepsy on sleep in children. METHODS: Whole night polysomnography was performed in 48 epileptic children and 12 healthy controls. The 48 epileptic children were divided into focal seizure and generalized seizure groups and into waking seizure and sleeping seizure groups according to the time of occurrence of the seizures. Various parameters of sleep structure were analyzed. RESULTS: The sleep efficiency of epileptic children was significantly lower than that of the healthy controls (85.4 ± 8.6% vs 90.9 ± 5.8%; P<0.05). The total recording time (TRT) of sleep was significantly longer and the sleep efficiency was significantly lower in the focal seizure group compared to the control group (P<0.05). The percentage of stage 1 non-rapid-eye-movement sleep (S1 sleep) increased and the percentage of rapid-eye-movement (REM) sleep decreased in the generalized seizure group compared to the control group (P<0.05). The percentage of S1 sleep increased and both the percentage of REM sleep and the sleep efficiency decreased in the sleeping seizure group as compared with the control group (P<0.05). There were no significant differences in the parameters of sleep structure between the waking seizure and the control group. Among the sleeping seizure group, the children with generalized seizure showed significantly lower REM sleep percentage and sleep efficiency, and those with focal seizure had significantly longer TRT and higher S1 sleep percentage as compared with the controls. CONCLUSIONS: Epilepsy affects sleep structure of patients, and different types of seizure have different influences on sleep structure. Children with generalized seizure have prolonged light sleep and shortened REM sleep. When generalized seizures occur during waking, the increase of light sleep is more pronounced. While generalized seizures occur during sleeping, REM sleep reduction is more prominent. Children with focal seizures have decreased sleep efficiency. When focal seizures occur during waking, the sleep structure of patients is normal. However, when seizures occur during sleeping light sleep increases and sleep efficiency decreases.[Chin J Contemp Pediatr, 2007, 9 (1):6-10]