In order to determine the electronic factors that may affect the catalytic antioxidant activity of water-soluble metallocorroles a series of 10-aryl-5,15-pyridinium manganese-(III) corroles was prepared. These complexes were examined regarding the effect of the C-10, substituent on the Mn-IV/Mn-III redox potentials, catalytic rate constants for decomposition of HOONO, prevention of tyrosine nitration, and superoxide dismutase activity. This structure-activity relationship investigation provides new insight regarding the mechanism by which manganese(III) corroles act as catalytic antioxidants. It also discloses the superiority of the C-10-anysil-substituted complex in all examined aspects.