The polysiloxanes containing 5-fluorouracil were prepared by reacting diethylaminopoly-disubstituted siloxanes with 5-fluorouracil. The obtained polymers were structural characterized by IR and H-NMR spectra. The products were hydrolyzed in acidic

alkaline and neutral medium at room temperature respectively. The amount of 5-fluorouracil released was quantitated by measuring its UV absorbance at 266.5 nm. However in the case of polymers containing dimethylsiloxy ((CH3)2SiO-) moiety

their stabilities toward hydrolysis are inc reased as the value n increases. Polymers with Si-N- linkage (type A) hydrolyze more rapidly in acidic medium but slowly in alkaline medium than the polymers with Si-O-linkage (type B).