To explore the possibility that the intestinal motor response to feeding is intact even in infants with immature fasting patterns, we performed low-compliance, continuous-infusion manometry in 13 term and 23 preterm infants during the first postnatal week. Babies were fed a standard formula intraduodenally at 4 ml/kg/2 hr by infusion pump. Small bowel motility responded to feeding; fasting patterns were replaced with long periods of persistent activity. During the infusion of formula, there was no significant difference in motor activity between preterm and term infants. Four characteristics of motor activity changed with feeding: motility index, the number of pressure peaks per 30-minute period, mean amplitude of pressure peaks, and duration of periods of quiescence. The number of pressure peaks per 30-minute period was the most sensitive index of the motor response to feeding, and it was used to characterize the fed pattern response. The start and duration of the fed response were similar in both groups of infants. Thus, despite the presence of immaturity in fasting patterns, the intestine of the preterm infant responds appropriately to feeding. These data help explain why preterm infants usually tolerate antral feedings, and support their use.