Monoacetyldiglycerides purified from deer antler, and identical synthetic compounds, have been shown to stimulate hematopoiesis. In the present study, we synthesized eight monoacetyldiglycerides, one of which, 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (3), was structurally identical to one of the naturally occurring monoacetyldiglycerides and showed the most potent stimulation of hematopoiesis by colony forming unit in culture (CFUc) assay, having a stimulation index (SI) of 1.54+/-0.23 at a concentration of 1.0 microg/ml. Moreover, 1.0 microg/ml 3 showed potent growth-stimulation activities on megakaryocyte culture, long term culture of Lin(-)Sca-1(+) cells with irradiated MS-5 stromal cells (SI, 1.69+/-0.16), and on the number of cobblestone colonies (SI, 10.4+/-0.25). In a murine model, 3, at concentrations of 0.5, 5 and 50 mg/kg/d, i.p. and p.o., effectively stimulated hematopoiesis in vivo 7 d after syngenic bone marrow transplantation of irradiated C57BL/6 mice, when assayed by the colony forming units in spleen (CFUs) assay. These data suggest that monoacetyldiglycerides may have significant clinical potential for the acceleration of hematopoiesis.