1. The electrical activity of the small intestine of conscious dogs, rabbits and sheep was recorded by means of chronically implanted electrodes and was related to mechanical changes in the bowel.2. A pattern of activity characteristic of segmental contractions (a prolonged series of bursts of spike activity superimposed on the basic electrical rhythm) was recorded successively at consecutive sites along the small intestine. This activity was as pronounced in the rabbits and sheep which were fed ad lib. as in the dogs which were fasted for 12 hr.3. The segmental contractions began in the duodenum and had a frequency of 15-20/24 hr. As they passed along the intestine, their velocity diminished and in the rabbits and sheep this was associated with an increased duration of activity. Most of the contractions reached the terminal ileum taking 1.5-2 hr in each of the species despite the differences in the length of the small intestine.4. The propagation of segmental contractions appears to be a normal and common activity of the intact bowel and it may have a propulsive as well as a mixing function.