A characteristic propulsive wave, previously reported in adults with ulcerative colitis, has been found in infants with acute diarrhea but not in children with ulcerative colitis. The reasons for this are discussed. The induction of propulsive wave forms in normal individuals by administration of magnesium sulfate orally is described and attention is called to its application to therapeutic studies. The relation of this wave form to propulsion of fecal contents and defecation and its role in the production of abdominal discomfort are considered. Observed variations in the responses of individual children to subcutaneous injection of Mecholyl®, to oral administration of iced water, and to rectal distention may explain innate differences in susceptibility to the development of colonic symptoms in different children. A classification of wave forms from the distal colon based on current concepts of their probable physiologic significance is offered. A tracing from the distal colon in a child having a spontaneous bowel movement is presented and commented on.