Behavioral and physiologic responsivity to nasogastric gavage feeding was assessed in 36 preterm infants on 2 consecutive d. On one of these days, a pacifier was provided during and after the gavage segment of the standardized protocol. The protocol was divided into segments that included baseline, preparatory handling, pregavagc, gavage, and postgavage periods. Patterns of cardiac (heart period and vagal tone), oxygen saturation, behavioral state, and defensive behavioral responses to gavage were quantified. These stable preterm infants responded to handling and gavage feeding with reductions in heart period, vagal tone, and oxygen saturation. These responses were not altered by provision of a pacifier, although there was a tendency for fewer episodes of bradycardia and oxygen desaturation. Conversely, behavioral state was affected significantly by nonnutritive sucking: when provided with a pacifier, infants exhibited less behavioral distress, spent less time in fussy and active awake states during and after feeding, and returned to a sleep state significantly faster. There is converging evidence to suggest that nonnutritive sucking lessens behavioral distress to iatrogenic stressors but does not alter physiologic responsiveness.