Reference electrodes utilizing cation exchanging qualities of perfluorosulfonic polymer membranes (Nafion) have been developed. They are constructed of a plastic body with Nafion plug connecting inner and outer compartments. The variability of the composition of filling solutions makes these electrodes suitable for applications where conventional reference electrodes cause interferring effects. Data on stability, reproducibility, effect of temperature, pH and total ionic strength of several cationic forms of the electrodes are presented.