Secondary neoplasms account for some 1.6-3.0% of solid malignancies encountered in surgical specimens from the genitourinary tract. At autopsy the proportion is higher, largely due to sampling bias. The peak incidence occurs around the seventh decade, and male and female incidences are approximately equal at all sites except the kidney, which shows a male preponderance owing to an excess of metastatic lung cancer. Adenocarcinomas are the most common histological type of secondary neoplasm and may be histologically and immunohistochemically indistinguishable from primary neoplasms arising from colonic-type epithelial metaplasia. Seeding of tumour along the urinary passages does not appear to be a significant mechanism of metastasis, and spread from one part of the genitourinary tract to another is uncommon. Clinical information and ancillary investigations are more helpful than special histological techniques in differential diagnosis.