The aim of this study is to elucidate the nature of ileal interdigestive contractile patterns by the computerized analysis of the contraction spread and by videofluoroscopy. Conscious dogs equipped with closely spaced strain-gauge force transducers were used. Two patterns of repetitive, phasic contractions were recorded, migrating clusters and phase IIIs; both patterns consisted of repetitive, propagated contractions. Both patterns migrated aborad by sequential movement of contraction waves down the bowel. Consequently, the rate of migration of either of the entire patterns was slower than the propagation velocity of constituent, individual contraction waves. Both patterns differed in several parameters, especially the propagated contractions of the clusters spread over shorter distances (1.47 +/- 0.4 cm) than those of phase III (4.65 +/- 0.99 cm). Compared with these complex patterns, propagating power contractions represented single contractions that propagated aborad at the same velocity as the contraction waves of the complex patterns. All three patterns propelled luminal contents distally.