Diazotisation of a substituted 7-amino-1,2,3-benzothiadiazole, followed by removal of the diazonium group by hypophosphorous acid or by a Sandmeyer reaction, may lead to a 1,2,3-benzothiadiazole containing an orientation of substituents different from that of the starting material. The occurrence of the rearrangement is governed by the nature and position of the 4- and 6-substituents of the original amino compound.