The structures of three triterpene alcohols isolated from the latex of Euphorbia antiquorum were established to be eupha-7,9(11),24-trien-3beta-ol (2; antiquol C), 19(10-->9)abeo-8alpha,9beta,10alpha-eupha-5,24-dien-3beta-ol (3; antiquol B), and 24-methyltirucalla-8,24(24(1))-dien-3beta-ol (4; euphorbol) on the basis of spectroscopic methods. Compounds 3 and 4 have previously been assigned the erroneous structures of 10alpha-cucurbita-5,24-dien-3alpha-ol and 24-methyleupha-8,24(24(1))-dien-3beta-ol, respectively. Compounds 2-4 and four other known compounds isolated from the latex, euphol (1), lemmaphylla-7,21-dien-3beta-ol (5), isohelianol (6), and camelliol C (7), showed potent inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA).