Hordenine is an ingredient of some plants which are used as feed for animals, i.e. in sprouting barley. After ingestion of such feed hordenine may be detected in blood or urine of horses which in case of racing horses may be the facts of using prohibited compounds. Results of some experiments in pharmacological models show that hordenine is an indirectly acting adrenergic drug. It liberates norepinephrine from stores. In isolated organs and those structures with reduced epinephrine contents the hordenine-effect is only very poor. Experiments in intact animals (rats, dogs) show that hordenine has a positive inotropic effect upon the heart, increases systolic and diastolic blood pressure, peripheral blood flow volume, inhibits gut movements but has no effect upon the psychomotorical behaviour of mice. All effects are short and only possible after high doses which are not to be expected after ingestion of hordenine containing feed for horses. A measurable increase of the performance of racing horses is quite improbable.