S-Allyl N-acylmonothiocarbamates react in boiling benzene with primary and secondary amines in the presence of catalytic amounts of triethylamine.In this reaction, the S-allyl group is replaced with the amino group under formation of N-acylurea derivatives in 45-90percent yields.The wide applicability of the reaction is demonstrated by the synthesis of eighty four N-acyl-N'-substituted and N-acyl-N',N'-disubstituted ureas with various aliphatic, aromatic and heterocyclic substituents.