Intestinal hyperperistalsis is one part of the clinical picture in infantile colic. Three gut hormones involved in the regulation of gut motility; motilin, vasoactive intestinal peptide (VIP) and gastrin, were measured with the RIA method in: 40 infants with infantile colic, (age 2-22 weeks), 42 healthy age-matched infants, 11 children (age 3-36 months) with gastrointestinal disorders, and 20 children (age 3-36 months) with non-gastrointestinal disorder. Basal s-motilin levels were raised in infants with infantile colic (p less than 0.01) and in children with other gastrointestinal disorders (p less than 0.001). Formula-fed infants had higher basal s-motilin levels than the breast-fed infants (p less than 0.05). P-VIP and s-gastrin levels were raised in children with other gastro-intestinal disorders (p less than 0.05), but not in infantile colic. Formula-fed colicky infants had higher s-gastrin levels than the breast-fed colicky infants (p less than 0.05). We suggest that the increased s-motilin level in infantile colic might account in part for the clinical picture of this disorder.