PURPOSE: Defecography is known to be a sensitive and specific measurement of pelvic floor dyssynergia (PFD). However, its standardized parameter for diagnostic analysis is still incomplete. We attempted to determine which defecographic findings are most significant for PFD, and how closely they match other physiologic tests and clinical symptoms of functional pelvic outlet obstruction. METHODS: Ninety-six patients with constipation who completed work-up of their symptoms with defecography, anorectal manometry and electromyography (EMG) were included in the study. Internal consistency of defecographic findings, and agreements between defecographic findings and results of other tests were statistically analyzed (Crohnbach's alpha, Cohen's kappa, respectively). RESULTS: Of the 96 patients evaluated, obstructive symptoms of constipation were obvious in 35 (36.5%) by obstructive symptom score. As known defecographic findings for PFD, poor opening of the anal canal was found in 33 (34.4%), persistent posterior angulation of the rectum in 33 (34.4%), and poor emptying of the rectum in 61 (63.5%). Manometric defecation index, manometric evacuation index, and EMG findings compatible with PFD were in 81 (84.4%), 72 (75%), and 73 (76%), respectively. Internal consistency of three defecographic findings was good (alpha = 0.78). Agreements between each defecographic findings and each result of other tests were all poor. CONCLUSION: Among known defecographic findings for PFD, one specific finding cannot be considered more important than the others for its diagnosis. It is hard to expect consistent results of various diagnostic tests and to predict the presence of defecographic PFD by use of anorectal manometry, EMG, or even by clinical symptoms.