When 1 first developed an interest in the pathology of bone 1 found that there were relatively few books on the subject available. Much of my information had either to be obtained from searching the journals or from senior colleagues in the field, who, 1 should add, were always more than willing to teach me. With this memory in mind, 1 have endeavoured to produce a book which 1 hope is of a convenient size and yet will hold sufficient information to be of use mainly to the pathologist faced with a bone problem. This is not intended to be an all-embracing source of knowledge on the subject; indeed, such a task could not be undertaken by a single author in these days of the rapid increase in information even in small subspecialist areas within bone pathology. Although this book is written mainly for the pathologist, it is hoped that it may also be of interest and value to orthopaedic surgeons, rheumatolog ists and radiologists. Most of the illustrations are original and many of the drawings are my own. There has been a long tradition of interest in bone pathology at The London Hospital, which has resulted in a wealth of material being available to me from the archives of the Department of Morbid Anatomy. A few of the photo graphs are those of Prof. H. Turnbull; the observant reader will detect these, since the scales used are not metric.