The evaluation of chronic constipation with or without encopresis must begin with a careful history. The intervals between bowel movements and the size and consistency of stools deposited into the toilet should be noted. Encopresis may be manifested as dirtying the underwear. The physical examination should include a rectal and neurological examination. No specific organic cause can be found in the majority of children. One or several anorectal physiological abnormalities have been found by us and others in 95% of children with idiopathic constipation. These abnormalities include impaired rectal and sigmoid sensation and decreased rectal contractility during rectal distention. The external anal sphincter and pelvic floor muscles may be abnormally contracted during straining for defecation, and the child may be unable to defecate a rectal balloon. Most patients will benefit from a program designed to clear stools, to prevent further impaction, and promote regular bowel habits. Fifty percent of patients will be cured after 1 year and 65%-70% after 2 years.