The electrochemical study of N-tert-butoxy-2,4-diphenyl-6-tert-butylphenylaminyl (1a), N-tert-butoxy-2,4-bis(4-chlorophenyl)-6-tert-butylphenylaminyl (1b), N-[2-(methoxycarbonyl)-2-propyl]-2,4-diphenyl-6-tert-butylphenylaminyl (2), and N-tert-butoxy-2,4,6-tris(4-chlorophenyl)phenylaminyl radicals (3) was performed by cyclic voltammetry using acetonitrile as the solvent and Bu4NPF6 as the supporting electrolyte. On cathodic scan (100mV/s), all the radicals gave chemically reversible cyclic voltammograms, and the E 1 / 2 red s were determined to be −1.405V (1a), −1.310V (2a), −1.282V (2b), and −1.195V (3) (versus Fc+/Fc), respectively. On anodic scan (100mV/s), on the other hand, 1a, 1b and 2 showed chemically reversible cyclic voltammograms, but 3 exhibited a partially reversible couple even on a scan rate of 500mV/s, indicating that the cation species of 3 was less stable. The E 1 / 2 ox s determined for 1a, 1b, 2 and 3 were 0.220, 0.280, 0.318 and 0.294V (versus Fc+/Fc), respectively. The electrochemical data were compared with those of thioaminyl radicals, the corresponding sulfur analogues of 1–3.