Four isolates, A1, C1, D3, and F2, from the ethanol extract of the green leaves of Plumeria acuminata Ait, showed antimutagenic activity. The antimutagens were isolated from the bioactive hexane and carbon tetrachloride fractions following a bioactivity-directed fractionation scheme and using the micronucleus test to monitor the antimutagenic activities. Structure elucidation studies indicated that C1 is stigmast-7-enol[1], D3 is lupeol carboxylic acid [2] and F2 is ursolic acid [3]. The structure of A1 was not fully elucidated but MS data suggested that it contained a long hydrocarbon chain. At a dosage of 2 mg isolate/25 g mouse, A1 reduced the number of micronucleated polychromatic erythrocytes (MPCE) induced by the mutagen, mitomycin C, by 75%, C1 by 80%, D3 by 57%, and F2 by 76%. Compound A2 was also isolated but was found inactive. Its structure was identified to be lupeol acetate [4].