A virus derived from cells of a lymphoblastoid line originating from the lymph node of a healthy African green monkey was characterized as a typical member of the foamy virus subgroup of retroviridae by its morphological, physicochemical, biological and biochemical properties (reverse transcriptase activity). Besides the usual host range of foamy viruses, the isolated strain revealed a remarkable T-lymphotropism, distinguishing it from the prototypes of foamy viruses previously isolated from African green monkeys. Two foamy virus infections are demonstrated in human contacts of the African green monkey colony, with the animal harbouring the isolate.