Fowl tampans (Argas persicus) collected in Oktemberyan in the Armenian S.S.R. in 1974 were found to be massively infected with rickettsiae of the spotted fever (SF) group. One isolated rickettsial strain, designated Armenia 9, is antigenically related to, and probably identical with, strain Armenia 11 and strain B of Rickettsia slovaca, isolated from Dermacentor marginatus ticks. Strain Armenia 9 grows readily in chick embryo yolk sacs and in chick embryo cell (CEC) and L-cell cultures. It causes generalized infection in both soft and hard ticks. A fatal disease was produced in Clethrionomys glareolus after subcutaneous inoculation. Similar inoculation of other small wild rodents (Mus musculus, Microtus arvalis, Apodemus flavicollis), hens and laboratory animals (guinea pigs, white mice and hamsters) resulted only in an antibody response.