Continuous perfusion manometry was performed in 31 preterm and term infants to assess the influence of gestational age on small intestinal motility. Gestational ages ranged from 27 to 42 weeks. All 8 term infants had interdigestive cycles that included all three phases. Only 4 of 23 preterm infants had complete interdigestive cycles. The remaining 19 preterm infants had only periods of motor quiescence and nonpropagating contractions. In term infants the interdigestive cycle was significantly shorter and the amplitude of phase 3 activity was significantly greater (p less than 0.01); velocity and duration of phase 3 activity were similar in both groups of infants. Rhythmic nonpropagating activity, or clusters, made up more than 60% of the phase 2 activity in both term and preterm infants. Although clusters did not propagate across three or more leads, approximately 25% of cluster activity was propagated across two leads. The duration of total cluster activity was similar for all gestational ages, but the frequency of clusters decreased and the mean duration of individual clusters increased with gestational age (both p less than 0.01). The amplitude of individual pressure peaks in clusters and phase 3 increased significantly with gestational age (p less than 0.03 and p less than 0.01, respectively). The motility index also increased with gestational age (p less than 0.02). We conclude that small intestinal motility is more immature in preterm infants than in term infants. Furthermore, cluster activity, which increases in duration and amplitude with gestational age, may be an immature form of phase 3 activity. These data and techniques will provide neonatologists with a direct way of tracking preterm intestinal motor function to provide more appropriate enteral nutrition.