This new edition reflects advances in the diagnosis and classification of bone tumours made over the 20 years since the first edition appeared. Although still based on routine light microscopy, the revised classificationbenefits from immunohishemical and molecular biological findings. It discusses new entities, such as intraosseous well differentiated osteosarcoma, round-cell osteosarcoma, and clear-cell chondrosarcoma. It deals with the difficulties of diagnosis within the group of malignant roundcell tumours,such as the distinction between Ewing sarcoma and primitive neuroectodermal tumour of bone. These changes update the classification to facilitate the comparison of data both nationally and internationally.