The aim of this study was to describe the etiological, clinical, rectoanal manometric findings as well as the results of biofeedback therapy in a series of 65 patients (34 males, 31 females, aged between 5 and 77 years) presenting with severe primary constipation due to pelvic abdominal asynchronism. Pelvic abdominal asynchronism was statistically more frequent in males during childhood and in female patients during adult life (p less than 0.005). This study disclosed a high frequency of psychogenic factors in the onset of pelvic abdominal asynchronism (26 p. 100) as well as a high frequency of soiling (46.2 p. 100) in constipated patients. In 36.2 p. 100 of cases, pelvic abdominal asynchronism was the only abnormality. In contrast, in most of the patients, asynchronism was associated with miscellaneous rectoanal disorders: increased anal closure pressure (43.3 p. 100), decreased anal closure pressure (11.8 p. 100), impaired rectal conscious sensitivity (11.7 p. 100), and increased rectal compliance (31 p. 100). This study demonstrated that when high-fiber diet and laxatives fail, biofeedback therapy is a very interesting alternative, providing 80 p. 100 of good results in selected cases. However, we were unable to find any clinical or manometric parameters predictive of results of treatment. Follow-up studies are needed to determine long-term results of biofeedback training.