The authors describe the results of the cloning of hemopoietic cells from 85 patients with different patterns of nonlymphoblastic leukemias in the agar drop--liquid medium system. It is shown that measurement of the colony-stimulating activity of hemopoietic cells and their growth pattern as well as morphological study of the cultures can be employed in practical hematology for making diagnosis and differential diagnosis, for evaluation of the treatment efficacy and prediction of the disease prognosis. The presence of blast colonies, an increase in the number of cell aggregations is regarded as an unfavourable prognostic criterion. Elevation of the colony-stimulating activity of hemopoietic cells is evidence of a more favourable prognosis.