Cultures of umbilical cord blood and mobilized peripheral blood mononuclear cells were carried out in a stirred bioreactor with pH and dissolved oxygen control. Expansion of total cells and colony-forming units granulocyte-macrophage was greatly enhanced by the use of a cell-dilution feeding protocol (as compared to a cell-retention feeding protocol). The specific oxygen consumption rate (q(O2)) for these cultures ranged from 1.7 x 10(-8) to 1.2 x 10(-7) mu mol/(cell.h). The maximum in q(O2) for each culture closely corresponded with the maximum percentage of progenitor or colony-forming cells (CFCs) present in the culture. The maximum q(O2) values are slightly less than those reported for hybridomas, while the lowest q(O2) values are somewhat greater than those reported for mature granulocytes. Examination of the ratio of lactate production to oxygen consumption in these cultures suggests that post-progenitor cells of the granulomonocytic lineage obtain a greater portion of their energy from glycolysis than do CFCs. The different metabolic profiles of CFCs and more mature cells suggest that monitoring the uptake or production of oxygen, lactate, and other metabolites will allow estimation of the content of several cell types in culture.