A method for coupling bleomycin A5 to oligonucleotides is proposed. The reaction was carried out between an amino group of a spermidine residue of the Cu(II) complex of bleomycin A5 (Cu(II)Blm-RH) and a 5'-phosphate group of the oligonucleotides d(pCCAAACA) (I), d(pCGTCCTC) (II), d(pT)16 (III), d(pCAAACA) (IV), and d(pGCCAAACA) (V) activated with a mixture of triphenylphosphine and 2,2'-dipyridyl disulfide in the presence of 4-(N,N-dimethylamino)pyridine 1-oxide. The yields of the products Cu(II)Blm-R-d(pCCAAACA) (Ia), Cu(II)Blm-R-d(pCGTCCTC) (IIa), Cu(II)Blm-R-d(pT)16 (IIIa), Cu(II)Blm-R-d(pCAAACA) (IVa), and Cu(II)Blm-R-d(pGCCAAACA) (Va) were 60-80%. After removal of the Cu(II) ion from the bleomycin A5 oligonucleotide derivatives Ia-IIIa, compounds Ib-IIIb were obtained. Compounds Ia, IVa, Va, and Ib-IIIb were further used for modification of the target d(pTGTTTGGCGAAGGA) in the presence of Fe(II) ions and 2-mercaptoethanol. Site-specific cleavage of the target by Blm coupled to complementary oligonucleotides was demonstrated. It was shown that efficiency and position of cleavage of the complementary reagents Ia, Ib, IVa, and Va are determined by their oligonucleotide part while the action of thenoncomplementary reagents IIb and IIIb was similar to that of the free antibiotic.