Apart from the previous report, the reaction of 3‐(4‐nitrobenzoylformamido)‐4‐(4‐nitrophenyl)‐1,2,5‐thiadiazole (2a) with m‐chloroperbenzoic acid in chloroform at room temperature did not proceed, whereas at reflux temperature the same reaction gave 4‐nitrobenzoic acid (5) (86%) and a minute amount of a mixture of 4‐nitrobenzoylformamide (6) and 3‐amino‐4‐(4‐nitrophenyl)‐1,2,5‐thiadiazole (7a). On the other hand the same reaction in a mixture of ethanol and chloroform (1:4) at room temperature gave 3‐ethoxycarbamoyl‐4‐(4‐nitrophenyl)‐1,2,5‐thiadiazole (8a) (24%) as an isolable product. When 3‐aroylformamido‐4‐aryl‐1,2,5‐thiadiazoles 2 in tetrahydrofuran were treated with various alkoxides in the corresponding alcohols at room temperature, 3‐amino‐4‐aryl‐ 7, 3‐alkoxycarbamoyl‐4‐aryl‐ 8, and 3‐aryl‐4‐(aryl)(hydroxy)acetamido‐1,2,5‐thiadiazoles 9 were isolated. The ratios of which were dependent on the kind of bases and the solvent employed. Selected compounds 2 were allowed to react with phosphorus pentasulfide in the presence of pyridine at reflux to give 3‐aryl‐4‐arylacetarnido‐1,2,5‐thiadiazoles 17 (55–64%), which were also produced by the reaction of 2 with either Lawesson's reagent or hydrogen sulfide gas in the presence of pyridine at reflux.