dc conductivity (sigma) studies were carried out for various types of ethylene ionomers in the temperature range from room temperature to 400 K. Ionomers used in this study are metal salts (Na, K, Mg, Ca, Co, Cu, Mn, and Zn) of poly(ethylene-co-methacrylic acid) (EMAA) and transition-metal complexes with 1,3-bis(aminomethyl)cyclohexane (BAC). It was revealed that the conduction behaviors certainly reflect the state of ionic aggregation. In particular, the sigma vs the reciprocal of temperature plots for all the ionomers studied exhibited a maximum peak or an inflection near 325 K. The temperature exhibiting this anomaly coincided with an order-disorder transition temperature of ionic aggregates (T(i)), and moreover, the anomaly was observed as a peak for ionomers with a microphase separation of the ionic aggregates from the polymer matrix, while it was observed as an inflection for ionomers without the microphase separation. Thus, this study uncovered an interesting fact that the sigma anomaly near 325 K is widely observed for EMAA ionomers and the appearance of the anomaly is markedly dependent upon a microphase structure of the ionomers.