Sleep apnea has been recorded in many infants, but little data exist concerning the amount and range of apnea in infants. We studied 49 infants referred to the sleep disorders unit. Single polysomnographic studies were performed on each infant. We examined the amount of apnea, presence and amount of upper airway obstruction and the sleeping pattern in each infant. Central apnea was common to all infants and varied in amount. Upper airway obstruction, recorded as mixed apnea, was found in 36 infants. Twenty of these infants had only occasional mixed apnea ( < 2 apneas/hour), whereas 16 infants displayed a higher amount of obstruction. All infants were separated into two groups according to amount of apnea and obstruction. Sixteen infants with obstruction plus 3 infants with a high amount of central apnea represented group I. The remaining 30 infants represented group II. Marked differences in the sleeping pattern were found when the groups of infants were separated. Infants from group I had significantly less rapid eye movement (REM) sleep than infants from group II. We conclude that sleep-disordered breathing in infants is associated with disruptions in sleep.