Investigation on the EtOH extract of the fruits of Chaenomeles speciosa led to the isolation of a new triterpene acid bearing an unusual hydroperoxyl substitute group at C-11, speciosaperoxide (1), along with six known triterpenoids, 3beta-acetoxyurs-11-en-13beta,28-olide (2), 3-O-acetyl ursolic acid (3), oleanolic acid (4), ursolic acid (5), masilinic acid (6), and tormentic acid (7), and three known norsesquiterpenoids, roseoside (8), vomifoliol (9) and (6S,7E,9R)-6,9-dihydroxy-4,7-megastigmadien-3-one 9-O-[beta-d-xylopyranosyl (1 --> 6)-glucopyranoside] (10). Their structures were elucidated on the basis of spectroscopic data and comparison with reference data. Besides compound 1, compounds 2, 8-10 were obtained from this genus for the first time. None of these compounds exhibited inhibitory activity against T-and B-lymphocyte proliferation.