Oligofecorrhea is the term applied for infrequent defecation (2 or less stools per week). 146 patients with oligofecorrhea were studied. Investigations comprised radiologic, endoscopic, intestinal transit and rectal pressure studies. EMG for levator and sphincteric muscles as well as internal sphincter biopsy were done. The 146 patients could be categorized into 3 stages according to clinical and investigative results. However, the 3 stages share major abnormal findings which comprise high resting rectal neck pressure, reduced or absent recto-inhibitory reflex, internal sphinter hypertrophy and degeneration of the nerve plexus of the internal sphincter. A new theory of pathogenesis of oligofecorrhea is put forward. It is believed that innervation abnormalities of the internal sphincter interferes with the recto-inhibitory reflex action with a resulting failure of the internal sphincter to relax upon rectal distension. It seems that the degenerative changes of the nerve plexus affect mainly the parasympathetic supply leading to sympathetic overactivity. The latter leads to abnormal internal sphincter contraction which eventually results in muscle hypertrophy. Internal sphincter myotomy showed a mean improvement of 90.4% in all the cases. The stool frequency and rectal neck pressure were normalized.