Viruses of Leishmania have recently been identified and characterized. These viruses are consistently double-stranded RNA viruses of approximately 5 kb. To date, they have not been reported to exist outside their protozoan host, nor have they been shown to be infectious. We report here the ability to transiently transfer these viruses to two strains of Leishmania, one previously infected and one that did not previously carry a virus. A PCR-based assay was used to detect viral negative-stranded RNA. Input RNA was ruled out as the source of template because a replication-incompetent (UV inactivated) virus was not detectable after transfer into Leishmania.