We have investigated the colony-forming capacity (CFC) of fetal liver cells(FLC) and it sensitivity to different growth factors (GF) in 15 healthy fetuses of 14-22 weeks gestation age (active period of haemopoiesis in the liver). Our results were compared with the same characteristics of bone marrow cells (BMC) from 19 children without haemotological diseases. The method of cell cultivation in agar gel was used. Human leukocytes, cord supernatant, IL-3 and GM-CSF (Schering-Plough, USA) and IL+GM-CSF served as GF. FLC CFC with GM-CSF was maximal 40.8 ± 5.4 per 2×105 cells, and did not depend on the gestation age of fetuses. Colony/clusters ratio was 2,7. CFC with human leukocytes and IL-3+GM-CSF was a little lower, but significantly less than under stimulation by IL-3 (11,2±2,2 per 2×105). The number of cells in colony was 100 - 500. There were granulomonocytic, macrophagic colonies. Most part of clusters was eosinophilic and macrophagic. BMC CFC with human leukocytes was 82,5±7,0 per 2×105 cells with colony/clusters ratio 0,8. The number of cells in colony was < 100. There were granylocytic, eosinophilic and mixed colonies. The results have been the same with other GF. We conclude that the big size of colonies formation and it predominance are suggestive of high proliferative activity of CFC from FLC as compared with BMC. Both types of cell were sensitive to all used GF, exept IL-3.