Strain gauge recordings of the motility of the antrum, duodenum, and jejunum were made in 10 dogs receiving a daily meal of canned food. Addition of 30 g of either wheat bran, cellulose, or guar gum increased the duration of the postprandial pattern of motility by 41-54% in the duodenum. Only cellulose and gum caused increases in the duration of the postprandial pattern of motility in the jejunum. The normal postprandial pattern of duodenojejunal contractions consisted of bursts of 4-10 rhythmic contractions. When bran or cellulose were added, the bursts were prolonged (12-15 contractions per burst) with 4-15 min intervals between bursts. In contrast, when gum was added, contractions occurred continuously at a rate of 7-8/min, but their amplitude was one-half that seen with the other fibers. The increased number of low amplitude contractions when gum was added caused the postprandial motility index to double. There was no change in the motility index when cellulose was added. Guar gum also increased the frequency of antral contractions by 129%, while bran and cellulose had no effect. Jejunal transit time and flow of digesta were measured in four dogs 2 h after the meal. Addition of bran or gum increased the transit time by 28% and 51%, respectively, but cellulose caused a 900% increase in transit time associated with a 50% reduction in the flow of digesta. Addition of different fibers causes different alterations in postprandial motility. Jejunal transit of digesta appears unrelated to the pattern of contractions.