STUDY OBJECTIVES Although the American Academy of Sleep Medicine (AASM) mandates that periodic limb movements during sleep (PLMS) be scored on every polysomnogram, and considers a periodic limb movement index (PLMI) > 5/h abnormal in children, there is a lack of community-derived data regarding the prevalence of PLMS in children, and no data to support this cutoff value. Therefore, the aim of this study was to determine the prevalence of PLMS in a sample of normal children. DESIGN Retrospective study. PARTICIPANTS 195 healthy, non-snoring children aged 5-17 years, recruited from the community, who underwent polysomnography for research purposes. METHODS PLMS were scored using the AASM 2007 criteria. MEASUREMENTS AND RESULTS The group age (median [IQR]) was 12.9 [10-15] years, and 58% were male. Sleep architecture was normal, and the obstructive apnea hypopnea index was 0.1 [0-0.3]/h. The median PLMI was 0/h, ranging from 0 to 35.5/h. Fifteen (7.7%) subjects had a PLMI > 5/h, and only 3 (1.5%) met the adult pathologic criterion of more than 15/h. Use of the 95th percentile PLMI cutoff of 7.2/h produced little difference in categorization between groups. Children with a PLMI > 5/h had a higher arousal index than those with a lower PLMI (11.6 [8.8-14.6] vs 8.1 [6.1-9.9]/h, respectively, P = 0.003). CONCLUSIONS This study provides normative data to the field and supports the clinical periodic limb movement index cutoff of > 5/h based on both prevalence and the correlate of increased sleep fragmentation. Periodic limb movements during sleep are infrequent in normal children recruited from the community. CITATION Marcus CL, Traylor J, Gallagher PR, Brooks LJ, Huang J, Koren D, Katz L, Mason TB, Tapia IE. Prevalence of periodic limb movements during sleep in normal children.