The effect of the type of alkali metal cation on the conductivity and ion transport mechanism is analyzed for PEGME-MClO4 electrolytes (where M = Li, Na, K, Rb, Cs). The data are obtained in the wide alkali metal perchlorate concentration (from 10(-5) to 5 mol/kg PEGME) range. The obtained results evidenced that at salt concentrations less than 10(-3) mol/kg higher conductivities are obtained for Li, Na, and K perchlorates, whereas at salt concentrations greater than 1 mol/kg conductivities measured for Cs and Rb perchlorates are higher. At intermediate salt concentration ranges, conductivities measured for all systems are similar. The observed trends are supported by the viscosity and IR results describing the ion-ion and ion-polymer interactions. The formation of ionic associates is additionally monitored by the application of the Fuoss-Kraus formalism to the salt concentration dependence of the molar conductivity.