Objective To explore aescin's inhibition of in vitro proliferatim in L1210 murine acute lymphoid leukemia cells and its in vivo antileukemic effects.Methods MTT assay was used to determine the anti-proliferative effect in vitro;Leukemia transplant models were used to test the antileukemic effect. Mice inoculated with L1210 cells were treated with ten daily doses of aescin or/and each other day of DOX, and were observed for survival.Antileukemic effects were assessed by calculating the extension of lifespan. Results Aescin(20～60?g/mL) was found to be able to inhibit the proliferation of L1210 cells.The effects were in a dose- and time- dependent manner.The IC_(50) value of aescin in L1210 cells after 72 h was (24.86?2.23)?g/mL.In vivo study showed that after treating the L1210 cells bearing mice with higher, middle,and low dosage(4.5,3.5,and 2.5 mg/kg) of aescin for ten consecutive days,The extension of lifespan were 25.8%(P