The transport of hydrogen counterions was studied in solutions of a linear polyelectrolyte, chondroitin sulfate, CS, by voltammetric measurements at a platinum disk microelectrode. The use of microelectrodes enables voltammetry of the counterion in solutions with little or no supporting electrolyte over a wide range of polyelectrolyte concentrations. The voltammetric interactions of counterions with polyions diminish transport-limited current for reduction of electroactive counterions, as shown by comparing results for a polymeric strong acid, poly(styrenesulfonic acid), and simple strong acids. The experimental results agree reasonably well with Manning’s theory, which describes the effect of ionic interactions on the transport of simple ions in the presence of polyelectrolytes. The data agree equally well with a much simpler semiempirical theory. The experimentally determined limiting value (no supporting electrolyte) of the transport ratio, D/D-0 is 0.53, where D and D-0 are the diffusion coefficients of free hydrogen ion with and without CS. The pK(2) of the carboxyl group of CS is estimated to vary from 3.5 to 5.7 in the range 0.1-0.001 M of ionic strength.