Most commonly, constipation in the infant is functional, with increased tone of colonic smooth muscle. Hirschsprung's disease is the best known of the infrequent organic causes. Treatment includes reassurance of parents, use of sugars, fluids and bulk and care of fissures. Voluntary stool withholding occurs in older children, who present with a variety of symptoms. Medicines are required to restore the functional capacity of the colon after chronic distortion by stool. This must be combined with psychologic help.