The structure of shidasterone, the phytoecdysone isolated from Blechnum niponicum (Blechnaceae) has been studied. In connection with this, stereoisomers of the cholestane-20, 22-diol derivatives in regard to C-20 and C-22 have been synthesized and their chemical and spectral properties have been examined. Chemical and physico-chemical data and, in particular, the 13C NMR spectrum of shidasterone have revealed that shidasterone is identified as 22, 25-oxido-5β-cholest-7-en-6-one-2β, 3β, 14α, 20-tetraol (1).