Chlamydiae-like, streptomycin-resistant parasites have been isolated from a high percentage of embryonated snow goose eggs collected at various stages of incubation; the agents stained specifically by immunofluorescence with antiserum against psittacosis and multiplied intensively in the yolk sacs of chicken embryos and induced in mice the production of antibodies that reacted in complement-fixing (CF) tests with a psittacosis group antigen. The isolates showed a high infectivity, but a low pathogenicity for chick embryos and mice. High doses of the isolate produced no cytopathic effect (CPE) in cultured mouse peritoneal macrophages and L cells. Release of lysosomal acid phosphatase did not occur in the inoculated macrophages throughout the time of observation.