Adult liver has a complex defence system that is critical in protection against infectious challenge. Its role in tumour surveillance is poorly understood. Because of its location, function and complex blood supply, the liver will be exposed to metastatic cells generated anywhere else in the body. Moreover, the role of the liver in detoxification can result in the generation of products with carcinogenic properties. It should not be surprising, then, to discover that the liver has a specialized immune system tailored to protect against and respond to significant immunological challenge, particularly metastasis and malignancy. This tumour surveillant role is the focus of this review.