The prevalence of primary nocturnal enuresis (PNE) in children aged 7 years, is about 5-10%. This study aims at finding the relation between PNE and sleep architecture. The study included 20 children with PNE & 10 healthy control children. All patients & controls undergone clinical, polysomnographic and urodynamic assessment. Results revealed a statistically significant longer delta wave sleep and less awakenings in patients compared to controls. We concluded that PNE may be due to a NREM sleep disorder with difficult arousal.