New derivatives of daunorubicin (DRB), doxorubicin (DOX), and epidoxorubicin (EDOX) with an amidine group bonded to C-3' of daunosamine moiety with either morpholine or hexamethyleneimine ring attached to the amidine group are studied in this paper. We have shown that all of these newly synthesized anthracycline derivatives inhibit human leukemia K562 cell line proliferation but only some of them induce erythroid differentiation when used at subtoxic concentrations. Morpholine derivative of DOX has the greatest potential to inhibit proliferation and to induce differentiation in vitro. The correlation between these two cellular processes was also significant for other tested compounds. In cell cycle analysis, we have demonstrated that those anthracycline derivatives that exert the greatest cytostatic potential caused G(2)/M arrest, which in turn, might contribute to the development of a differentiating phenotype. The concentrations of the compounds used in the study are pharmacologically relevant. These new potent inducers of differentiation might be exploited as anticancer drugs for treatment of leukemia by differentiation therapy.