1. Two unrelated families with a genetically determined arthritis-like syndrome of the joints of the hand and wrist are described.

2. The condition begins before puberty, is relatively painless and is not functionally disabling. The condition resembles that described by Thiemann and appears to fall into the group of avascular necrosis.

3. The appearance of the abnormality is controlled by a single autosomal gene which manifests itself in nearly all persons who are heterozygous for it. Two of the offspring of a marriage between affected persons showed much greater involvement than their siblings.

This suggests that they may represent the effect of the abnormal gene in double dose. If this is so, the type of inheritance cannot strictly be regarded as "dominant," since the abnormal homozygote is different from the heterozygote.