A virus, referred to as the Innisfail strain, was isolated by mouse inoculation horn a naturally Infected water-rat, Hydromys chrysogaster, captured in north Queensland, Australia. It was shown to be indistinguishable from the EMC vims of Helwig and Schmidt by cross-neutralization and cross-complement fixation tests, and was considered to belong to the EMC group of viruses.Mice and guinea-pigs were highly susceptible. Rats showed signs of paralysis, but usually survived. Rabbits and three-day-old chickens were resistant.Infection of mice was characterised by paralysis and death in 2-3 days, and encephalitis and myositis were the prominent histopathological features. Heavily infected guinea-pigs died within 3-7 days, with encephalitis and seveie macroscopic myocarditis. This is believed to be the first report of natural infection with a virus of the EMC group in Australia.Toxoplasma was also isolated from the water-rat, making a new host record.