Three new lanostane-type triterpenoids, inonotsutriols A (1), B (2), and C (3) were isolated from the sclerotia of Inonotus obliquus (Pers.: Fr.) (Japanese name: kabanoanatake; Russian name: chaga). Their structures were determined to be (3b,21R,24S)-21, 24-cyclolanost-8-ene-3,21,25-triol (1), (3b,21R,24R)-21,24-cyclolanost-8-ene-3,21,25-triol (2), and (3b,21R,24S)-21,24-cyclolanosta-7,9(11)-diene-3,21,25-triol (3) [15], and platelet-aggregation inhibitory activity [16]. Recently, we reported the structures of five new lanostane-type triterpenoids isolated from the sclerotia: inonotsuoxides A and B ((3b,22R,24S)-22,25-epoxylanost-8-ene-3,24-diol and its (22S)-22,25-epoxy epimer) [17], and inonotsulides A, B, and C ((3b,20R,24S)-3,25-dihydroxylanost-8-en-20,24-olide, and its (20R,24R)-20,24-olide epimer, and (3b,20R,24S)-3,25-dihydroxylanosta-7,9(11)-dien-20,24-olide) [18] and the antitumor promoting activity of intodiol which is the most abundant triterpene in this sclerotia. Careful examination of the sclerotia of I. obliquus has led to the isolation of three new lanostane-type triterpenes named inonotsutriols A (1), B (2), and C (3). The structures of the new compounds 1 -3 were determined on the basis of NMR spectroscopy, including 1D and 2D ( 1 H,