This review presents a brief account of the chemistry and mechanistic aspects of aryl H-phosphonates, and selected applications of this class of compounds as intermediates in the synthesis of a wide range of biologically important analogues of nucleoside phosphates, and oligonucleotides, in which the phosphate moieties are replaced by other structurally related groups. The aryl nucleoside H-phosphonates, compounds of controlled reactivity, have proven to be more versatile and superior to various mixed anhydrides as synthetic intermediates, particularly for preparation of nucleotide analogues bearing P-N or P-S bonds in various configurational arrangements at the phosphate moiety.