Three cases of the abdominal pain, which are derived from the rectus abdominis, were presented. The abdominal pains of unknown origin are frequently misdiagnosed as arisen from visceral sources. That brings inappropriate diagnostic tests and unsatisfactory treatments. If patients have no intraabdominal cause, we must pay attention to the possibility that patients with abdominal pain may suffer from this presumed nerve entrapment syndrome or myofacial pain syndrome. Rectus abdominis syndrome is causes by entrapment of an anterior cutaneous branch of one or more thoracic intercostal nerves. Myofacial pain syndrome is defined as the sensory, motor and autonomic symptoms caused by the myofacial trigger points. The authors report three cases of abdominal pain caused by trigger point in the rectus abdominis muscle. On physical examination, trigger points in the rectus abdominis muscle were found, and abdominal pain was successfully treated by trigger point injections.