Since the publication of the third series in 1994, there has been a revolution in our understanding of the clinical, pathologic, and molecular features of tumours in the kidney, bladder or related urinary structures . Thus, it is fitting that this volume should be the first in the fourth series. In the fourth series in general, and in this fascicle in particular, there is an increased emphasis on new molecular findings which are relevant to diagnostic tumour pathology, as well as on the diagnostic features of aspiration and exfoliative cytopathology. Differential diagnosis is also emphasised, and numerous tables summarise important differential diagnostic considerations, including the appropriate roles of immunohistochemical stains. Important recommendations for gross dissection and surgical pathology report construction are also included. The authors have expanded the previous edition by approximately twenty per cent, and almost all of the 586 illustrations are now in colour. The 1530 references in five chapters are comprehensive and up to date.