In order to gain an understanding of the lytic activity of sea cucumber saponins, turbidity change according to the theory of Bangham and Mie with minor modification was observed. The effect of purified sea cucumber saponins on the initial osmotic swelling behavior, which has a linear relationship with the reciprocal of the serially diluted lipid concentration of the liposomes, was also studied by exposing the liposome to hypotonic glucose solution. The lysis phenomena due to the interaction of sea cucumber saponins with phospospholipid multilayered liposome seems to be dependent on the presence of cholesterol component, especially. Also structural differences of the terminal sugar moiety of these saponins, particulary the number and the position, have influence on the lytic activity. All these saponins increased the initial swelling rate of cholesterol-containing liposome. But in cholesterol-free liposome, the two saponins except Echinoside A which has also lytic activity on liposome without cholesterol, do not have significant in fluence on the initial swelling rate in comparison with Echinoside A.