Phosphonated carbocyclic 2'-oxa-3'-azanucleosides have been synthesized and tested for their antiretroviralactivity. The obtained results have shown that some of the compounds were as powerful as azydothymidinein inhibiting the reverse transcriptase activity of the human retrovirus T-cell leukemia/lymphotropic virustype 1 and in protecting human peripheral blood mononuclear cells against human retrovirus T-cell leukemia/lymphotropic virus type 1 transmission in vitro. These data indicate that phosphonated carbocyclic 2'-oxa-3'-azanucleosides possess the necessary requirements to efficiently counteract infections caused by humanretroviruses.