Forty-three apneic episodes were observed in eight preterm infants, four of whom had a history of spells. Measurements of expiratory airflow and respiratory effort indicated that 36 of 43 spells were mixed, consisting of central apnea preceded or followed by airway obstruction. The episodes occurred more frequently during periods of spontaneous neck flexion. This association can be related to previous studies indicating that neck flexion interferes with neuromuscular regulation of pharyngeal patency and can produce intermittent airway obstruction. Our observations suggest that airway obstruction may be an important factor in the pathogenesis of apnea in certain preterm infants.