1. Five cases of this rare developmental anomaly—congenital annular defect—varying in degree and type are reported.
2. In one patient the main annular groove was fairly deep and situated as high as the level of the pelvis at the root of the lower limbs. There were also multiple congenital defects associated with this anomaly.
3. Literature on the subject, especially from the point of view of etiology, has been reviewed.
4. It has been suggested that most of the so-called congenital amputations may not be actual amputations, and that these actual amputations are unrelated in etiology and pathology to circular constriction.