The high degree of isolation of Antarctica may well have protected its seals and birds from many of the diseases found in related species outside the continent. Our recent review of diseases in penguins has shown that birds taken into captivity are susceptible to a wide range of diseases, many of which have not been recorded in the wild. The same situation presumably applies to Antarctic seals. Adélie penguins in Antarctica have been shown to have antibodies to Newcastle disease virus, avian influenza virus and the Chlamydia group of bacteria. From this we could infer that wild birds have had contact with these diseases but, in the cases of viral diseases at least, a more likely explanation could be that the antibodies are the result of cross-infection with related but benign viral strains. There is no evidence to date that any major exotic diseases have been introduced into the Antarctic ecosystem. However, unless non-pathogenic strains are present to provide cross-immunity, all birds and seals are likely to be highly susceptible to such introductions.