The aim of this study was to describe the polysomnographic features of childhood-onset narcolepsy. A retrospective review was performed on children with narcolepsy. The polysomnogram findings were compared with reference values obtained from normative data in the general population. Narcolepsy subjects had a mean initial sleep latency of 10.9 min on nocturnal PSG, which was shorter by a mean of 18 min than corresponding values from normative data (P < 0.001). Short initial REM latency on nocturnal PSG correlated with the number of SOREMPs on MSLT in subjects with narcolepsy (P= 0.007). These findings may assist in the clinical diagnosis of narcolepsy.