1. Thirteen aneurysmal bone cysts which have been subjected to extensive roentgenographic and histological study are reported.
2. The diagnosis of an aneurysmal bone cyst must be made on the basis of careful clinical, roentgenographic, and pathological studies.
3. Various modalities of therapy depending on the site of the lesion have been employed, and include curettage and bone-grafting, resection, and radiation therapy.
4. There was recurrence in one of the thirteen patients. The lesion in a metacarpal bone of a seven-year-old white boy recurred after a second curettage and bone-grafting but then gradually "healed out."
5. An extensive aneurysmal bone cyst involving the cranium showed evidence of arteriovenous abnormalities by angiography.
6. The clinical and pathological findings in our cases suggest that an aneurysmal bone cyst is essentially a reaction of bone to expanding vascular channels of unknown etiology.