The Association Internationale de Recherche sur la Circulation Osseuse, A.R.C.O., was founded in London in December 1989 by a small group of doctors, surgeons and researchers in basic sciences who had been involved for many years in the study of bone circulation and its disorders. They had met several times in Toulouse, during the International Symposia on Bone Circulation held there since 1973 and they wished to carry their contacts further. In founding A.R.C.O., they established as their primary aims the encouragement and furtherance of research, organisation of meetings and promotion of knowledge on the subject. At the present time, the Association has over a hundred