Some podands, acyclic polyethers, were utilized as membrane active components to prepare Ag + -selective polymeric membrane electrodes. The thiapodand-based electrodes exhibited considerable selectivity toward Ag + over other heavy metal ions including Cd 2 + , Pb 2 + , Cu 2 + and Hg 2 + . Also, good selectivity over alkali and alkali earth metal ions were observed. Response slopes, pH effects, response time, and signal baseline return of the sensor systems were studied in static mode and/or in a flow-injection system. The Ag + -selectivity was explained by the soft-soft interaction of the Ag + ion with the sulfur donor atoms as well as the stacking interaction between aromatic end groups of the host molecule on complexation.