M-3 murine myeloid leukemic cells undergo terminal divisions making colonies in methylcellulose culture and also renew themselves in methylcellulose and suspension; leukemic clonogenic cells are characteristic as stem cells. The effects of 1-beta-D-arabinofuranosylcytosine and four anthracyclines (Adriamycin, daunomycin, aclacinomycin A, and 4'-epidoxorubicin) on M-3 leukemic clonogenic cells were studied. 1-beta-D-Arabinofuranosylcytosine was effective in reducing primary and secondary colonies in methylcellulose and the growth of clonogenic cells in suspension. In contrast, the anthracyclines were not so effective in reducing secondary colonies in methylcellulose or clonogenic cells in suspension as to suppress primary colonies in methylcellulose. The results suggest that 1-beta-D-arabinofuranosylcytosine but not the anthracyclines is effective for not only terminal divisions but also self-renewal of leukemic clonogenic cells. The study will be used as a practical screening test to examine the effects of antitumor agents on leukemic blast progenitors.