This study characterizes the migrating spike complex (MSC) in the small intestine of the awake fasting cat and compares the MSC with interdigestive activity in the small intestine of other species. Electrical activity in each of 12 cats with implanted electrodes showed MSCs, bands of spike potentials which attenuated slow-wave frequency and amplitude as the MSCs progressed distally. MSCs occurred at variable frequency with intervals ranging from < 1 min to > 5 h and averaged 51.2 +/- 2.8 (SE) min. MSCs migrated at 1-8 mm/s, accelerating distally; the duration decreased distally such that the length of the bowel in a burst (2-3 cm proximally) was conserved. The MSC was associated with an intense prolonged contraction of duration similar to that of the MSC. Sometimes the MSCs occurred in close association, and when an MSC period was < 5.7 min, the second MSC propagated at a slower rate than the first. Frequently, a brief series of slow wave-associated spikes preceded an MSC. MSCs were not associated with slow waves. The MSC differs in several respects from the migrating myoelectric complex of other laboratory animals and is more appropriately classified in a category that includes giant migrating spikes, prolonged propagated contractions, power contractions, and migrating action potential complexes.