1. By the surgical division of the main capsular artery supplying the upper femoral epiphysis of the rabbit it is possible to cause changes which resemble those occurring in human osteochondritis.

2. The phase of anaemia (ischaemia and hypovascularisation) lasts in the rabbit less than fifteen days. The whole process lasts approximately ninety days, and only for one-sixth of this period does the femoral head suffer from a reduction in its blood supply.

3. After the fifteenth day until the end of the process the condition changes to one of hypervascularisation, which lasts six times longer than that of ischaemia or relative anaemia.

4. By the ninetieth day the whole process has lost its activity and only some permanent deformities remain. The vascular pattern is from then on the normal in the rabbit.

5. The "osteochondritic" changes cannot be elicited in the distal femoral epiphysis. The apparent reason is the presence of anastomoses between the main artery and other epiphysial vessels.

6. There seems to be reasonable experimental evidence, by implication, in favour of the vascular theory of osteochondritis of the upper femoral epiphysis in children.