The invention refers to a synthetic double-stranded oligonucleotide having a length comprised between 10 and 50 bases and a nucleic acid sequence selected from the group consisting of: (a) sequences corresponding to a selected portion of the promoter of human .gamma.-globin gene; and (b) sequences corresponding to a selected portion of the human genomic region comprised between the .gamma.-globin gene and the .delta..beta.-cluster, for use as an inducer of erythroid differentiation.