A series of electrochemical experiments employing a platinum sensing electrode have been carried out to investigate the relationship between Mn(III) dissolution and the rechargeable performance of the alkaline gamma-MnO2 electrode. The formation of soluble Mn(III) species was first investigated in relation to the redox reactions occurring during the two-electron cycling of gamma-MnO2, and its sensitivity established. The extent of Mn(III) dissolution during deep discharge cycling was then determined, and the level of soluble Mn(III) related to capacity fade, the formation of secondary phases and the implications for rechargeable performance. Finally, the inclusion of barium hydroxide in the electrode blackmix was shown to dramatically reduce the extent of Mn(III) dissolution, resulting in significant improvements in capacity retention and confirming previous suggestions as to its role in electrode rechargeability. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.076212jes] All rights reserved.