Bone marrow (BM) cells from 15 patients with chronic granulocytic leukemia (CGL) and 12 normal donors were placed in liquid culture for 4-7 days in the presence of fetal calf serum (FCS) or human AB serum. BM cells were plated in agar for GM-CFC growth at day 0, day 4, day 7 of culture, in the presence of human placenta conditioned medium (HPCM). The recovery of GM-CFCs on day 4 in FCS was 86 +/- 18 and 15 +/- 18% from normal or CGL BM cells respectively (p = 0.005). The recovery of GM-CFCs on day 4 in human AB serum was comparable for normal (66 +/- 48%) and CGL (69 +/- 32%) BM cells. Similar results were obtained on day 7 of culture. Cytochemical staining of agar plates showed a sharp drop of macrophage colonies in CGL BM cells kept in FCS cultures on day 4-7, when compared to both normal BM cells and baseline colonies. These data suggest that the survival in liquid culture of GM-CFCs from patients with CGL is dependent on a factor present in human and not in fetal calf serum. This is not the case for normal GM-CFCs.