The invention relates to compositions comprising double-stranded oligonucleotides of identical or different sequences and/or length, said oligonucleotides having sequences 3&prime；N1N2 . . . Ni-1Ni . . . Nj5&prime； wherein&mdash；3&prime；Ni . . . Nj5&prime； is half of a double-stranded 19-28mer oligonucleotide of sequence complementary to a target nucleic acid sequence present in a living cell, and&mdash；3&prime；N1 . . . Ni-15&prime； is a 3-50mer overhang of sequence allowing oligomerization of said double-stranded oligonucleotide. Compositions of transfection comprising said oligonucleotide compositions and there used for therapeutical application.
