The use of antisense oligonucleotides as a therapeutic tool in modulating gene expression represents a newly established strategy for treating diseases. Such oligomers may be designed to complement a region of a specific gene or messenger RNA. Using this approach, oligonucleotides can serve as a potential block of transcription or translation through sequence-specific hybridization with targeted genetic segments. In the Fourth Meeting of the Italian Society of Experimental Hematology "Discutiamone Insieme", authors reported the use of in vitro synthesized oligonucleotides to inhibit normal and chimeric gene expression of bcl-2 in normal and neoplastic cell lines, respectively, that carry the t(14;18) translocation. The roles of c-myb and B-myb in the control of the proliferation and differentiation of normal hematopoietic cell lines have been investigated by selective inhibition of the expression of specific transcripts. To get some insight into the correlation between proliferation and differentiation in myeloid cells, some authors studied and reported the differentiation potential of G1-arrested cells obtained by a specific oligodeoxynucleotide complementary to the 5' region of the c-myb mRNA. The use of anti-P53 antisense oligos in the modulation of the growth of normal and neoplastic bone marrow progenitors was presented and confirmed the pivotal role of this gene in cell cycle control. The role of abl gene expression in normal and chronic myelogenous leukemia (CML) cells is not yet completely understood. Selective inhibition of this proto-oncogene and of the abl-bcr oncogene have been achieved by using of c-abl sequence specific antisense oligonucleotides; this approach sheds new light on the function of this gene in CML.(ABSTRACT TRUNCATED AT 250 WORDS)