Disclosed are polymeric compounds which are useful as prodrugs, comprising a chain of monomeric nucleosides, nucleoside analogs or abasic nucleosides, wherein at least one of the nucleosides or nucleoside analogs or a heterocyclic derivative thereof is pharmaceutically active and the nucleosides, nucleoside analogs or abasic nucleosides are linked by a phosphodiester group, a phosphorothioate group or an H--, alkyl or alkenyl phosphonate group.