Alisol A monoacetate, alisol B monoacetate, alisol C monoacetate and alisol B were isolated from Alismatis Rhizoma, which is a herbal drug used frequently in the oriental prescriptions. Potential liver-protective activities of the isolated alisol compounds were evaluated against CCl₄-induced liver damage. The results obtained from liver microsomal enzyme assay, measurement of serum glutamic pyruvic transaminase (EC 2.6.1.2) and serum triglyceride content indicated that alisol A,B and C monoacetates showed significant liver-protective activities against CCl₄ poisoning. Alisol B monoacetate exhibited slightly higher activity than that of alisol B.