Electrophilic additions of phenylsulfenyl chloride or phenylselenenyl chloride to a carbon-carbon double bond of C-5,6 region of uracils in the presence of silver reagents such as Ag2O, AgBF4, or AgOCOCF3 directly gave the corresponding 5-phenylsulfydryl- or 5-phenylselenenyl uracils in good yields.