The alkaloids, dioscorine and dioscine, both obtained from yams, have been compared in respect of their convulsant activity, toxicity, analeptic action, local anaesthetic activity, adrenaline potentiating action, antidiuretic effect, and anti-acetylcholine activity. The alkaloids have similar properties, but in most respects dioscorine was the more potent. Aqueous solutions of dioscine are unstable.