The electrochemical oxidation of 2-phenyl-1,2-benzisothiazol-3(2H)-ones and related compounds was studied by conventional and mciroelectrode techniques. Hammett plots were drawn for a series of N-aryl substituted 2-phenyl-1,2-benzisothiazol-3-(2H)-ones and compared with those of the selenium analogues, 2-phenyl-1,2-benzisoselenazol-3(2H)-ones. Controlled potential electrolysis furnished the corresponding sulphoxides and the reaction pathway was shown to proceed through an ECE mechanism.