Two new lanostane-type triterpenoids, 1 and 2 besides two known lanostane-type triterpenoids, 3 and 4 were isolated from the sclerotia of Inonotus obliquus. Their structures were determined to be lanosta-8,23E-diene-3beta,22R,25-triol (1) and lanosta-7:9(11),23E-triene-3beta,22R,25-triol (2) by spectral data. These compounds were tested for their anti-tumor-promoting activity using a short-term in vitro assay for EBV-EA activation induced by TPA. Compounds 1, 2 and 4 were stronger than the positive control, oleanolic acid. The most abundant compound 4 was investigated for the inhibitory effect in a two-stage carcinogenesis test on mouse skin using DMBA as an initiator and TPA as a promoter. Compound 4 was found to exhibit the potent anti-tumor promoting activity in the in vivo carcinogenesis test.