Constipation and disordered defaecation are symptoms, not disease entities. Usually these symptoms are not caused by organic abnormalities, but by disordered motility of the colon and pelvic floor. Both decreased colonic motility (inertia coli) and increased frequency and amplitude of haustrating colonic contractions in the context of an irritable bowel syndrome may lead to constipation. A third important functional cause of constipation is by paradoxical straining of the pelvic floor muscles during (attempts to) defaecate: anismus. In the diagnosis of constipation the primary aim usually is the exclusion of organic disorders. A plain abdominal X-ray and measurement of colonic transit with radiopaque particles will provide information about the severity of the constipation. Defaecography is indicated primarily if disordered faecal expulsion exists. Anorectal manometry is relevant when Hirschsprung's disease is suspected.