Seven kinds of 4-substituted 5-(5-nitro-2-furyl) thiazol-2-ones were obtained by the reaction of α-substituted β-(5-nitro-2-furyl) vinylamines (Ia-g) with chlorocarbonylsulfenyl chloride. Reaction of Ia and c with trichloromethylsulfenyl chloride gave 3-sub-stituted 4-(5-nitro-2-furyl)-5-chloroisothiazoles.