The condensation aligomers of 5-fluorouracil were ppepared by reacting 2，4 bis-(trimethylsilyloxy) 5-fluoropyrimidine with various dicarboxylic chlorides，e．g．The structural eharacteristics of the ohgomers obtained were investigated by IR．1HNMR．The oligomers were then hydroly zed in acid．alkaline and neutral medium at room temperature respectively and the amount of 5．fluorouracil released was guan-titated by measuring its absorbanee at 266.5nm. However．in the case of oligomers containing phenylene moiety，5-fluorouraeil was not detected，when the hydrolysis was conducted in acid or neutral medium．while in the case of oligomers containing methy-lene moiety，hydrolysis proceeded readily in acid，alkaline and neutral medium．