The alkylation of 6-(polyfluoro)alkyl-2-thiouracils with 4-bromobutyl acetate in refluxing acetonitrile in the presence of K2CO3 proceeds regioselectively to give S,O-disubstituted pyrimidines as the major products and S,N-isomers as the minor ones, whereas the use of 2-bromoacetophenone as an alkylating agent results in the formation of the S,O-isomer. 6-Trifluoromethyl-2-thiouracil and 2-(2-oxo-2-phenylethylthio)-4-(2-oxo-2-phenylethoxy)-6-trifluoromethylpyrimidine exhibited marked tuberculostatic activity. 6-Trifluoromethyl-2-thiouracil did not exert a significant cytotoxic effect on the HeLa cell culture and human dermal fibroblasts.