There is provided inter alia use of 2′,3′-dideoxy-3′-hydroxymethylcytidine or a prodrug or salt thereof in the manufacture of a medicament for the treatment of HIV infection wherein the reverse transcriptase of the HIV bears at least one mutation that allows an obligate chain terminating nucleoside- or nucleotide phosphate to be excised from the nascent DNA strand by ATP- or pyrophosphate-mediated excision.