SUMMARYBorrelia queenslandica, n. sp., was isolated from Rattux villosissimus Waite in northwestern Queensland. It produced a relapsing type of infection, sensitive to antibiotics, in laboratory rats and mice. Immunity developed after primary infection in mice. Guinea‐pigs and young chickens resisted infection but the organism could be maintained in embryonnted eggs. A human volunteer inoculated with 75–100 million B. queenslandica did not become infected.