The aim of this study was first to examine the effects of 24-h sleep deprivation on apnea index and duration in lambs. The effects on sleep architecture and sigh and swallowing indices were also studied. The impact of postnatal maturation on all measured variables was assessed by studying two different age groups. Twelve lambs (six aged 1-2 d and six aged 23-24 d on the day of surgery) were chronically instrumented for polysomnographic recordings including sleep state assessment, nasal flow, diaphragm electromyogram, and glottal constrictor muscle electromyogram. Two recordings, one control and one after 24-h sleep deprivation, were performed in all lambs. Results show that the effects of sleep deprivation predominate in rapid eye movement sleep in the younger group, with increased rapid eye movement sleep proportion and apnea, sigh, and swallowing index. Our results in lambs suggest that the consequences of sleep deprivation upon respiration are predominant early after birth. Although the potential relationship of these observations to neonatal apneas and sudden infant death syndrome has yet to be defined, awareness of the effects of sleep deprivation is important for neonatal care.