It is universally accepted that with the cessation of airflow, the infant is technically apneic, but the significance of such respiratory "pauses" remains a matter of discussion. Central apnea is easily recognized, but the absence of airflow with continued "respiratory" movements is commonly interpreted as obstructive apnea. The respiratory pattern of individual normal and abnormal infants was studied in depth. Airflow was monitored using a recently devised facial plate thermistor system; chest movement was recorded by measuring changes in thoracic impedance. On several occasions, esophageal pressure was also recorded as was expired CO2. Using the above systems, it was confirmed that mouth breathing in the infant is confined to periods of crying or yawning, and that many "obstructive" episodes merely represent straining against a closed glottis during movement.