The known sesquiterpene valeranone (= Yatamanson) was isolated from the subterranian parts of Nardostachys yatamansi (DC). It was pharmacologically investigated in animal experiments of sedative, tranquilizing and antihypertensive properties. In some experiments, typical for tranquilizers, certain activities could be demonstrated such as the prolongation of barbiturate hypnosis, the impairment of rotarod performance, an anticonvulsive activity on electric shock and potentiation of the body-temperature lowering activity of reserpine. In three other pharmacological models an anti-ulcer action was detected. In general the activity of valeranone was lower than those of the standard substances used. As regards the hypotensive property only a weak activity was demonstrated. In toxicological studies on rats and mice an oral LD50 of greater than 3160 mg/kg was found, which suggests the possibility of a therapeutically useful dose ratio.