In the preface to the First Edition the authors stated that "Histochemical techniques are now an essential part of the histopathological diagnosis, in a restricted number of conditions, their use however have not yet gained wide acceptance". Seven years later, histrochemistry is firmly established as an indispensable tool in routine diagnosis, covering a wide specturm of pathology. Its role has now greatly expanded to encompass diagnosis, prognosis and monitoring response to therapy. The authors were encouraged by the response of colleagues to the first edition and, seven years later, when techniques have changed or improved, others developed and new pathology areas become important, the authors felt that a new edition, incorporating in particular immunopathology, which was deliberately restricted to the well-established areas in the first edition, would be of value. In this second edition, the layout has changed slightly, some chapters have been omitted as they became irrelevant, others adapted to the recent developments and new chapters introduced. A comprehensive guide to immunohistochemical methods has been included as a new chapter and an appendix. Fine needle aspiration cytology has its advocates and is a rapidly expanding diagnostic technique: methodology, interpretation and caveats are described and discussed in a new chapter. Antibody studies in soft tissue tumours, in their infancy in the first edition, are now a major part of the diagnosis and have been integrated into a new chapter. Lymphomas are extensively covered in the second edition. This is one of the fields where the development of an increasing number of monoclonal antibodies has led to new concepts of disease and classification, with important implications is clinical management. The authors have attempted to avoid duplication which has arisen in immunological discussion in many of the chapters, but have left the paragraphs where the content was particularly relevant. Immunohistochemistry in routine diagnosis, in its early stages included in the first edition is now a well-established method of diagnosis. Here also included in the second edition is information on in situ hybridization, flow cytometry and other areas which have just started having an impact in diagnostic pathology and are thought to be important in the future.