Spontaneous nonfeeding swallows taken during wakefulness and sleep were identified in nine preterm infants by characteristic patterns in pharyngeal pressure, submental electromyogram, and respiratory airflow. Two hundred and seventeen swallows during ongoing respiration interrupted either inspiratory or expiratory airflow with airway closure for approximately 1 s. The duration of airway closure was independent of respiratory rate. A brief "swallow-breath" was associated with swallow onset in most instances. The respiratory nature of this movement was confirmed by simultaneous recording of a fall in pharyngeal or esophageal pressure and outward movement of the abdomen. Prolongation of the respiratory cycle was generally observed when a swallow interrupted ventilation at higher lung volumes, i.e., in late inspiration or early expiration. When the swallow interrupted ventilation at lower lung volume, i.e, in late expiration or early inspiration, the subsequent inspiratory effort was usually obstructed as it preceded airway opening at the end of the swallow synergism.