In 1988 we presented our Guide to Bone Marrow Transplan tation. The reception has been enthusiastic and we have re ceived a flood of critical comments, suggestions and requests to provide an update in due time. Although several books on marrow transplantation have recently been published, their scope and goal have generally been different. Hence, we have decided to prepare a second edition of the Guide. Our aim was to maintain a short, concise text which never theless would incorporate changes that have occurred over the past four or five years. We have streamlined the description of...