In endemic VE virus habitats at Sontecomapan and nearby Arroyo Agrio, Veracruz, México, four species of wild mammals were infected, based on isolation of virus, and six species probably were infected based on antibody tests. Virus was isolated at Sontecomapan during August 1963 from tissues or blood of two opossums (Didelphis marsupialis and Philander opossum) and one bat (Artibeus turpis), and during May 1966 from another bat (Carollia subrufa). Hemagglutination-inhibition (HI), neutralization (N), or complement-fixation (CF) tests with VE virus detected antibodies at Sontecomapan in these mammals and also in Glossophaga bats, Peromyscus mice, Rattus rats, a rabbit, a raccoon, and a weasel, and in endemic habitats at Minatitlan, Veracruz, in Sigmodon cotton rats. The averages of positive-HI prevalences were .43 for wild terrestrial mammals and .17 for bats. Opossums and Artibeus jamaicensis bats were inoculated subcutaneously with VE virus in the laboratory and found to develop viremia within 2 or 3 days, which lasted through the 4th day after inoculation. Detectable N and HI antibodies, but not CF, appeared in serum of opossums within 9 to 30 days and HI antibody in plasma of bats within 10 to 35 days.