(i) The volatile oil from the wood of Chamaecyparis formosensis, Matsum., or Formosa cypress (benihi), contains much less terpenes and much more terpenes alcohols as compared with the volatile oil from the leaf of the same plant. (ii) The predominant terpenes in the oil are d-a-pinene and d-camphene, and they are optically strongly active. (iii) Among the terpenic alcoholic components there have been proved two new substances ‘benihiol’ C10H18O, and ‘benihinol’ C10H18O. (iv) In the sesquiterpene fraction, a new sesquiterpene whose hydrochloride has the melting point 103°–104°C. was isolated, and it was named sesquibenihene. (v) Among the sesquiterpene alcohol fraction, there are, along with a tertiary alcohol of cadinol type, at least one more primary alcohol the exact nature of which is not yet definitely known.