NEW MATERIAL:The silylalkylated 5-fluorouracil compound of formula I (R1 is silylalkyl of formula II; R2 is H or group of formula II; R3 is 1W4C alkyl or phenyl; R is 1W4C alkylene).

EXAMPLE: 1,3-Bis-(trimethylsilylmethyl)-5-fluorouracil.

USE: It has antitumor activity and is useful as a carcinostatic agent and antibacterial agent.

PROCESS: The objective compound of formula I can be prepared e.g. by suspending a base in a solvent, adding 5-fluorouracil to the suspension at room temperature to form a salt, adding the silylalkyl chloride of formula III thereto, and heating at 50W140°C. The base is preferably NaH, K2CO3, etc., and the solvent is preferably dimethylformamide.