Abstract: A practical method for the preparation of phthalylsulphathiazole developed in our laboratory which is adaptable for the commercial production of the drug is de- scribed. In this method water is used as a condensing medium: an amount of phthalic anhydride 10% in excess of the theory is added to a suspension of sul- phathiazole in boiling water all at once, then the mixture is kept at refluxing tem- perature for 4 hours. It is then filtered whilst hot, and the insoluble phthalylsul- phathiazole filter cake is washed with hot water to free it from the contaminated phthlic acid, and then dried. Yields of over 96% were obtained. The product con- formed to the assay requirements of the Chinese Pharmacopoeia, 1953.