The synthesis and antiviral evaluation of new acyclic phosphonate nucleosides related to HPMPC (Cidofovir) has been described. These aminopropyl phosphonate nucleosides 1-3 have an amino function within either the acyclic chain (series 2 and 3) or as substituent (series 1). Both purine and pyrimidine nucleotide analogues have been synthesized. In contrast to HPMPC the oxygen analogue of 2c, only a weak antiherpes virus activity could be demonstrated for 2b and 2c.