Nutritive and non-nutritive sucking was studied in 9 preterm infants with postmenstrual ages ranging from 28 to 33 weeks and postnatal ages ranging from 0 to 8 weeks. During nutritive sucking, sucking bursts were longer than sucking pauses. During non-nutritive sucking the opposite was seen. The sucking rate was lower during nutritive sucking. During nutritive sucking the respiratory rate was higher during the pauses than during the bursts. During non-nutritive sucking the respiratory rate was higher during sucking. It is concluded that non-nutritive sucking cannot serve as a model for studying feeding mechanisms in the preterm infant.