Soldado virus (TRVL 52214) is a new agent isolated from a pool of nymphal ticks of the Omithodoros capensis group (either O. capensis or O. denmarki ) collected from a Brown Noddy Tern ( Anous stolidtis) on Soldado Rock, Trinidad, in June 19(53. It is related to Hughes virus (isolates of which have also been recovered at the Rock) by complement-fixation test but not by neutralization test done in Vero cell cultures. Soldado virus kills infant and adult mice inoculated intracerebrally, but is not pathogenic for mice inoculated intraperitoneally.