Historically, defecatory disorders have been thought of as simply an abnormality of the outlet for defecation. Early terms used to describe this condition include anismus, pelvic floor outlet obstruction, or nonrelaxing puborectalis syndrome. It has become increasingly recognized, however, that there is no single criterion that can be used to diagnose a defecatory disorder, and that the mechanisms involved are more complex and extend beyond the anal sphincter. Previously, the role of the propulsive effort was underappreciated and was not addressed in earlier prospective studies of biofeedback therapy for constipation.