Chronic functional constipation is a common clinical disorder in pediatric age. Thirteen children with functional constipation were treated by administration of vegetable fibres together with a toilet training program, for two months. In each patient anorectal manometry showed presence of inhibitory anal reflex and diagnosis of constipation was confirmed by a prolonged gastrointestinal transit time measured by radio-opaque markers. In all patients there was a significant improvement in both stool frequency and intestinal transit time; furthermore, a normalization of anorectal motility variables was observed at rectal manometry. No changes in the blood levels of nutritional parameters were seen in any patient. It is concluded that vegetable fibres represent an effective treatment of functional chronic constipation in children.