Polymer electrolyte membranes (PEMs) are currently being evaluated for use in fuel cells, and hydrocarbon-based PEMs offer several advantages over perfluorinated polymer membranes (cheaper, show little methanol cross over and more tolerant to humidity conditions). Proton conductivities were measured for several hydrocarbon based polymeric blends that have been developed to incorporate both sulfonic acid and hydroxyl groups, or so called “inherently hydrated” PEMs: poly(styrene sulfonic acid/poly(vinyl alcohol-co-ethylene) (PSSA/PVACE), sulfonated styrene-butadiene-styrene triblock polymer/polyvinyl alcohol blend (SSBS/PVA), and sulfonated styrene-butadiene-styrene triblock polymer/polyvinyl alcohol (SSBS/PVPh). Proton conductivity was measured using two-probe and four-probe electrochemical impedance spectroscopy (EIS), carried out at RT on thin membranes soaked in double deionized water in the range of 106 Hz to 1 Hz with an AC amplitude of 10 mV. Blends of PSSA and PVACE had conductivities of 0.035 S/cm (25 wt. % PSSA), 0.01 S/cm (15 wt. % PSSA), and 0.007 S/cm (10 wt. % PSSA). By comparison, the proton conductivities of a perfluorinated polymer membrane, NafionTM, and the unblended SSBS (52% sulfonation) were 0.1 S/cm and 0.09 S/cm, respectively. SSBS/PVPh blends showed conductivities of 0.07 S/cm (85 wt. % SSBS) and 0.086 S/cm (95 wt. % SSBS), and SSBS/PVA blends gave 0.055 S/cm (60 wt. % SSBS) and 0.075 S/cm (78 wt. % SSBS). In general, ionic conductivities correlated with % sulfonation. Several procedural problems were resolved in applying the EIS to measure proton conductivity of membranes, and these included proper immersion depth, quality of deionized water, and ensuring proper electrode/membrane contact.