The amount and distribution of additive species in zinc alloy particles containing 0.025 wt % bismuth modified with 0.10 wt % indium for mercury-free alkaline manganese batteries were examined after storage at various discharging levels at 60 degrees C. The amount of hydrogen gas evolution due to the self-discharging reactions of zinc and the internal cell impedance were also evaluated. The amount of additive species in the zinc alloy particles was found to increase with increasing depth of discharge. Indium was homogeneously distributed on the surface even after partial discharge and also after storage for 1200 h at 60 degrees C. This behaviour is considered to contribute to the suppression of hydrogen gas evolution and increase in the internal cell impedance to the same level as when mercury is employed. As a result, mercury-free alkaline manganese batteries showed the same storage characteristics as conventional batteries containing mercury.