Abstract: The synthesis of a series of symmetrical bis-purines (Ⅶ) and bis-uracils (Ⅷ), in which the hydrogen atom of the mercapto group of 6-mercaptopurine (Ⅰ) and 5-mercaptouracil (Ⅱ) was replaced by different alkylene groups, were reported. Besides, several S-substituted 6-mercaptopurines (Ⅸ) were also synthesized. They were prepared by condensing the mercapto-compounds with suitable mono or dihalides in the presence of alkali. Preliminary pharmacological examinations showed that Compound Ⅶc was slightly active against sarcoma 180 in mice.