These experiments were investigated effects of the cell death of glycyrrhetinic acid (GA) on transplanted-L1210 cells in BALB/c mice. The GA suppressed the proliferation of L121 0 cells in vivo and in vitro system. The administration of GA induced apoptosis of transplanted-L1210 cells via the reduction of mitochondrial transmembrane potential in mice. The GA enhanced the production of nitric oxidation in peritoneal macrophages obtained from L1210 cells-transplanted mice. The apoptosis of L1210 cells were induced by co-culture of the macrophages obtained from GA administered mice and L1210 cells in vitro, and was partly inhibited by the treatment of L-NMMA. These results suggest that GA induces the cytotoxicity and the apoptosis of transplanted-L1210 cells via the production of nitric oxide in peritoneal macrophages.