The goal of this study was to clarify effects of sleep restriction on a diurnal rhythm of salivary cortisol and DHEA levels in Korean adolescents.83 middle school students were recruited to participate in restricted sleep period group (less than 4h/day) or unrestricted sleep period group (from 6h/day to 7h/day). Both were 14 to 17 years old. They were instructed to keep the sleep-awakening schedule and sampling protocol. Saliva samples of cortisol and DHEA were collected at 8h, 12h, 16h and 20h. Salivary hormones were analysed with salivary cortisol(or DHEA) EIA kit according to a fixed assay protocol. Cortisol levels of restricted sleep period group and unrestricted sleep period group significantly decreased according to the sampling times. Cortisol levels of sleep restricted group was significantly higher than those of usual sleep group at all sampling times. At 8h, DHEA levels of both groups were significantly higher than those at 12h, 16h and 20h. However, DHEA levels of restricted sleep period group did not differ from those of unrestricted sleep period group at all sampling times.Cortisol and DHEA levels of both group showed the typical diurnal rhythm regardless of sleep status. Restricted sleep may increased cortisol release, not DHEA release, which indicated a changed HPA axis.