Changes in the cytotoxicity of tetrandrine before and after liposome encapsulation on rat alveolar macrophages in vitro were ohserved. Results suggested that there was a siginificant differentiation on the adsorptive capacity to yeast, and the level in cytoplasmic free calcium and potassium, and the cytoskeletal control of macrophages at the concentration of 40?g/ml. Experiments showed that liposome encapsulation may attenuate cytotoxicity of tetrandrine.