A new 27-carboxylic lupane-type triterpene, tiarellic acid (1), was isolated from Tiarella polyphylla together with corosolic acid (2) and tormentic acid (3). Tiarellic acid was characterized as 3,23-dihydroxy-20(29)-lupen-27-oic acid and its NMR data were unambiguously assigned using 2-D NMR