Simian foamy virus (SFV) type 6, originally isolated from the kidney of a kuru-inoculated chimpanzee, has been adapted to produce an asymptomatic infection in Swiss-Webster white mice, with virus detected in the kidney and spleen for up to 10 months after intra-peritoneal inoculation, and the presence in some animals of complement-fixing, but not neutralizing, serum antibody. This first successful experimental infection of the laboratory mouse by a representative of the foamy virus group has special interest as a convenient model in which to study pathogenesis and viral latency, particularly in view of the isolation and recent characterization of a foamy virus from human tissue which is virtually indistinguishable from the SFV type 6 used in the present study.