[en] The hypothesis that clonal expansion of hematopoietic cells takes place in cultures with succession of functioning clones is tested in this investigation. CBA and CBAT6T6 mice of both sexes aged 8-12 weeks were used. The animals were irradiated with ¹³⁷ Cs gamma rays on an IPK apparatus in a dose of 12 Gy. Self-maintenance of a CFU-c was characterized by the number of daughter CFU-c produced by it in irradiated mice during the formation of an 11-day splenic colony. The results provide the authors with an argument in support of the view that CFU-c are incapable of true self-maintenance, but they are members of transient cell populations which mature consecutively, starting from certain earlier clonogenic precursors, or pre-CFU cells