Summary Sera obtained from a variety of domestic and wild animals and birds on Taiwan were tested for neutralizing and hemagglutination-inhibition antibodies with Japanese encephalitis virus antigen. Swine not only on Taiwan, but also on the Pescadore Islands and Okinawa, had a very high incidence of infection (80 to 100%). Antibody was found less frequently in all other species tested, but was present in a portion of the water buffalo, cats, rats, bandicoots, bats, herons and munias, and in one or two of several other species.