The effect of oral feeding on breathing pattern and ventilation was studied in 19 healthy term neonates in the semiupright supine position. Ventilation was measured with a nasal flowmeter, and sucking pressure via a modified nipple that permitted milk delivery. The feeding pattern in these infants consisted of an initial period of continuous sucking followed by intermittent sucking for the remainder of the feed. A significant reduction in minute ventilation (P less than 0.01) was observed during continuous sucking, and resulted entirely from a reduction in breathing frequency (P less than 0.01). Tidal volume did not change (P greater than 0.05), but prolongation of expiration (P less than 0.01) and shortening of inspiration (P less than 0.05) were also observed. During intermittent sucking, the minute ventilation was similar to that of the control period. However, smaller but significant changes in breathing frequency and in duration of inspiration and expiration persisted during intermittent sucking. Our results document a significant reduction in ventilation during the initial part of oral feeding in term neonates, and subsequent recovery with continued feeding. Depending on the magnitude of this reduction in ventilation, cyanosis and bradycardia may develop in some infants during oral feeding.