Constipation is a common condition defined by less than three bowel movements per week. Often constipation is secondary to altered motility of the colon. Tests that measure colonic motility lead the clinician to appropriate therapy. Colonic transit measured with either radionuclides or radio-opaque markers determine whether the transit through the colon is truly slow, and then identify the potential region of the colon that impedes the movement of intraluminal contents. Patients with normal colonic transit do not require further evaluation of their colonic motor function. Colonic and anorectal manometry differentiate patients in to 3 groups: (1) functional anal outlet obstruction; (2) uncoordinated distal colonic phasic contractions, and (3) colonic inertia. Functional outlet obstruction may be treated successfully by increasing the water content of their stools and biofeedback. Antispasmodics including anticholinergics, nitrates and calcium channel blockers may decrease the functional obstruction caused by phasic colonic contractions. The prokinetics such as cisapride have successfully improved constipation due to colonic inertia, Parkinson's disease or spinal cord injury as well as idiopathic inertia. Occasionally patients with inertia may require colectomy with ileorectal anastomosis to treat severe constipation.