Abstract: Paper chromatography of anthraquinone derivatives in Chinese rhubarb was investigated. It was observed that: 1. Carl Schleicher & Schule No. 2043b filter paper was shown to be superior to other grades used; 2. Of the 33 different solvent-systems tested, 8 were confirmed to be adaptable, of which a new one, carbon tetraehloride: benzene: water was found best; 3. The temperature effects on paper chromatography of anthraquinone derivatives were of little significance. Only R_f values of emodin and aloe-emodin slightly altered as temperature changed; 4. Horizontal technique with circular filter paper of 30 cm in diameter was considered to be more convenient than the ascending technique. The contents of anthraquinone derivatives in different species of Chinese rhubarb were determined quantitatively by the improved paper chromatography method. The results were as follows: 1. All the specimens of the same species examined exhibited approximately equal contents of anthraquinone derivatives, but those from different parts of the same species differed greatly. Duration of storage seemed to have no effect on the contents. 2. The anthraquinone derivatives varied greatly in quantity with each species: (i) Shih-Ning rhubarb (Rheum palmatum) had a higher content with a total value of 3.44— 3.47%, while the Liang-Chou species (probably Rheum Tanguticum) contained only 1.24%. (ii) Shih-Ning rhubarb had more emodin but less aloe-emodin, while the Liang-Chou species possessed a considerable amount of combined rhein but was devoid of aloeemodin and free rhein. (iii) Shih-Ning rhubarb showed a higher content of active principles of purgative and antibacterial action. It was, therefore, concluded that the Shih-Ning rhubarb was the best grade among those studied.