The transport of hydrogen counterions was studied in solutions of the strong polymer acid poly(styrenesulfonic acid) (PSSA) by voltammetric measurements at Pt disc microelectrodes. Use of voltammetric microelectrodes makes measurement possible in the absence of supporting electrolyte. Very strong interactions between counterion and polyion were observed under these conditions. Results obtained for polyacid solutions were compared with results for simple strong acids. The experimentally determined limiting value (with no electrolyte) of D/D0 was 0.345, where D and D0 are diffusion coefficients of counterion with and without PSSA. The dependence of hydrogen ion transport on concentration of electrolyte was studied over a range of polyelectrolyte concentrations from 0.05 to 1.05 mM. Any significant change in limiting value of D/D0 was not observed for examined PSSA concentrations. The influence of various supporting electrolytes (with mono-, di-, and trivalent cations and various anions) in a wide range of electrolyte concentrations on the interactions of counterions with poly(styrenesulfonate) ion was described. There are practically no differences in hydrogen ion transport for Li+, Na+, K+, Cs+, and TMA+. Distinct differences appear for TEA+. The influence of trivalent cations of the supporting electrolyte on the transport of hydrogen counterion in PSSA solution is stronger than the influence of divalent cations. The experimental results were compared with theoretical calculations and literature data for other monovalent counterions in polyelectrolyte solutions.