Chemical investigation of the root extract of Valeriana officinalis afforded a new bicyclic sesquiterpene acid, (-)-3 beta,4 beta-epoxyvalerenic acid together with valerenic acid and hexadecanoic acid. The structure of the new compound was elucidated by spectroscopic data and confirmed by partial synthesis of its methyl ester from valerenic acid. Methyl (-)-3 alpha,4 alpha-epoxyvalerenate was obtained as a minor product from the above reaction.