1. The pathological anatomy of osteochondritis dissecans of the hip is described, and its causation is discussed.

2. Eight new cases are reported.

3. The problems of treatment are considered.

1. The preparation of heterogenous grafts of calf bone is described.

2. The results of experimental application of such grafts in dogs and guinea pigs are recorded.

3. The results of eighty heterogenous grafts in humans are reported.

4. It is concluded that if the conditions are carefully controlled the results of heterogenous grafting are satisfactory.