This study was conducted to investigate the immuno-regulatory effect and apoptosis of L1210 and HL60 leukemia cells of methanol-extracts of Cornus kousa Burg(CKB). The proliferation of mouse splenocytes and thymocytes enhanced by the addition of 10 μg/ml of CKB. CKB were administered p.o. once a day for 7 days in adult male BALB/c mice. CKB increased the splenic and thymic T lymphocytes, especially the number of TH cells markedly increased by the treatment of CKB. CKB treatment induced the apoptotic cell death in L1210 mouse leukemia and HL60 human leukemia cells. In addition, CKB also accelerated the phagocytic activity in peritoneal macrophages and increased the production of plaque forming cells. These results suggest that CKB have an various immuno-regulatory property.