A study of cadaveric vertebral biopsy and a review of 100 clinical biopsies has shown that needles and trephines producing tissue specimens of two millimetres or more in diameter can be expected to give a high degree of diagnostic accuracy. The erythrocyte sedimentation rate was a more useful screening investigation than were estimations of serum alkaline phosphatase. The complications are described. It is suggested that patients with painful thoracic metastases and evidence of progressive cord compression should have early decompression after open biopsy if further neurological compromise is to be prevented.

1. Monostotic fibrous dysplasia in the long bones occurs most frequently in adolescence. In the jaws it is found mainly in early adult life. It presents later in the ribs, probably because it is often asymptomatic in this site.

2. The disease is equally distributed in both sexes.

3. Reactivation may occasionally occur in later life and in pregnancy.

4. Successful surgical treatment is by no means always easily achieved, and requires, in addition to the problems of fracture fixation and the correction of deformity, careful consideration of the age of the patient, the activity of the lesion and the extent to which it involves the cortical bone.

1 . A classification of Madelung's deformity on an etiological basis is suggested.

2. Seven patients with "idiopathic" Madelung's deformity and one occurring in association with Turner's syndrome are discussed.

3. Cytogenetic studies of five patients are recorded and their significance discussed.

4. Arthrodesis of the radio-carpal joint by the "wedge" technique is preferred for those patients whose symptoms warrant treatment.