The electrochemical behavior of hydrated manganese-substituted nickel hydroxides in Ni/Cd cells was studied. Partial substitution of manganese for nickel was shown to induce stabilization of the discharge capacity during long-term cycling. Such behavior is related to the very small discrepancy between the interslab distances of the oxidized material (gamma-phase) and the reduced material (interstratified phase I-E constituted of random distribution of gamma- and alpha-type interslab spaces), which strongly reduces the mechanical strains on cycling. Manganese also seems to slow noticeably the formation of the beta(III)/beta(II) couple on cycling, which was a crucial point for the homologous cobalt system, resulting in a significant decrease of the capacity vs. cycle number.