1. One case of spontaneous intra-uterine amputation and one case of spontaneous amputation occurring shortly after birth as a result of slough at a point of constriction have been presented.

2. Both cases presented illustrate associated constricting bands and subsequent osseous overgrowth of the amputation stump.

3. Spontaneous intra-uterine amputation, frequently associated with constricting bands of the other extremities, may be due to focal faulty development and is probably not due to amniotic bands or umbilical-cord encirclement. This type of late congenital limb absence differs from the absence due to limb-bud arrest. It is to be remembered that the limb buds appear on the truncal wall at four weeks after ovulation. The sequence of growth is from proximal to distal. The cartilaginous miniature of the extremity is complete at seven weeks after ovulation.

4. Osseous overgrowth of the stump in the spontaneous intra-uterine amputation is a phenomenon paralleling the overgrowth seen in children after a traumatic amputation.

5. The exact etiology of both types of congenital limb absence is not known. A genetic origin is probable. To date, there have been no reported studies regarding the possible role of chromosomal abnormalities in these entities.