Abstract: Potassium quisqualate has been isolated in crystalline form from the seeds of Quisqualis chinensis (Shih Chun Tze), a popular ascaracide in China. This salt has been proved to be highly toxic to earthworm. In order to investigate whether this salt possesses anthelmintic action, a clinical study of potassium quisqualate as well as raw or baked quisqualis seeds in comparison with santonin was made on 204 pa- tients with proved ascariasis. They were divided into 5 groups: One group received various dosages of 0.025, 0.050, 0.075, 0.100 and 0.125 gm of potassium quisqualate. The next three groups were given the seeds, raw or baked at 50°and 100℃, the amount of which varied with the ages of the patients. Those under twelve receiv- ed 5 gms, while those above twelve 10 gms of seeds. The last group received 0.120 gm of santonin. All were given without any laxatives. Each dose was given 2 hours after supper and before breakfast in the following morning. The number of ascarids in the stools was counted and recorded daily, and any observable side effects were also recorded. The results of this study indicate: (1) Potassium quisqualate possesses a definite anthehmintic action in patients. It may be considered as an anthelmintic principle of Quisqualis chinensis. (2) Without any laxatives, a dosage of 0.125 gm of potassium quisqualate produces highly anthelmintic action. The percentage of patients who excreted ascarids approaches nearly to that of those received santonin, and is greater than that of those received the raw or baked seeds. (3) The only drawback of using Quisqualis chinensis and potassium quisqualate is their side effect of causing hiccough. The side effect of the potassium salt is less marked than that of the raw seeds. The undesirable effect of the raw seeds decreases to some extent during the baking process.