Current study was designed to assess the functional etiology of patients with pelvic outlet obstruction. Moreover, physiologic characteristics and theirs clinical significances were evaluated in the patients with ramified diagnosis. METHODS: 172 patients with pelvic outlet obstruction were performed 328 numbers of physiologic studies. These included cinedefecography (n=172), anal manometry (n=87), colonic transit time study (n=38), and anal EMG/PNTML (n=31). On the basis of physiologic findings, patient groups were categorized as rectocele (group I), nonrelaxing puborectalis syndrome (group II), anal dyschezia (group III), and rectoanal intussusception (group IV). The physiologic findings were compared between subgroup patients. RESULTS: Incidence of categorized patients was 51.7% (group I, n=89), 22.7% (group II, n=39), 12.2% (group III, n=21), and 8.7% (group IV, n=15), respectively. The mean age of patients with group III were lower (p<0.05) than that of overall patients. The incidence of female patients was higher in group I and the incidence of male patients was higher in group II (p<0.0001). In cinedefecography, patients with group II showed smaller anorectal angle at strain (p<0.001), at dynamic change between rest and strain (p=0.002). In anal manometry, patients with group III showed higher mean resting pressures (p=0.001), higher maximum resting pressures (p<0.001), higher mean squeeze pressures, and higher maximal voluntary contraction (p=0.003) than those of patients with other group. In neurologic study, mean value of PNTML was 2.32 +/- 0.34 (range, 1.60~3.66) msec in overall patients. The size of rectocele was increased in proportion to patient's age (r=0.229, p<0.05), number of delivery (r=0.393, p=0.001), and degree of perineal descent (r=0.231, p<0.05). The degree of perineal descent was increased in proportion to patient's age (r=0.249, p<0.05). CONCLUSIONS: Present series provided the diagnostic ramification of pelvic outlet obstruction by using the anorectal physiologic investigations. In addition to the function of puborectalis muscle, evacuation dynamics of anorectum should be emphasized. These findings could provide the fundamental information for guideline of future therapy in the patients with obstructed defecation.