SUPERNUMERARY RIBS are uncommon. When present they usually arise from cervical or lumbar vertebrae, although sacral, coccygeal, intrathoracic, and aberrant lumbar ribs have also been reported. This paper concerns a patient who has 15 pairs of thoracic ribs arising from 15 thoracic vertebrae. In our search of the literature we have not found another case of a patient with this many pairs of thoracic ribs. The patient, a 35-year-old Caucasian man, was admitted for the first time to the University of Michigan Medical Center for an ileostomy to establish fecal control. A subtotal colectomy with an ileoproctostomy for Hirschsprung's disease at age thirty had been performed five years previously. Since then he had experienced persistent diarrhea and fecal incontinence. His history also included incision of a membranous imperforate anus shortly after birth. He had no complaints referable to his chest or back, and no structural abnormalities were evident on physical examination. The preoperative chest roentgenogr...