This review aims to illustrate the extent to which wildlife act as reservoirs of infections agents that cause disease in domestic stock, pet and captive animals and humans. Morc than 40 agents are described. In the case of some of these, e.g. Cryptosporidium spp., Escherichia coli O157 and malignant catarrhal fever, the current evidence is that wildlife either does not act as a reservoir or is of limited importance However, in the case of many important diseases, including bovine tuberculosis, Weil's disease, Lyme disease, avian influenza, duck virus, enteritis and louping ill, wild animals are considered to be the principal source of infection. Wildlife may be involved in the epidemiology of other major diseases, such its neosporosis. Johne's disease, mucosal disease and foot and mouth disease, but further studies are needed. The UK would benefit from a more positive approach to the study of wildlife and the infections they harbour. (C) 2002 Published by Elsevier Science Ltd.