The electrochemistry of a chemically prepared polypyrrole/poly(styrene-4-sulfonate) powder has been investigated by cyclic voltammetry and impedance! spectroscopy in a variety of aqueous electrolytes. The facile p-doping/undoping of thick layers of the polymer composite is shown to be due to the high ionic conductivity imparted by electrolyte solution in pores. As a consequence, the ionic conductivities of the polymer layers are strongly dependent on the concentration and conductivity of the electrolyte solution used but relatively insensitive to the doping level of the polymer. In contrast, electrochemically prepared polypyrrole/poly(styrene-4-sulfonate) films show much lower ionic conductivities with a pronounced dependence on doping level. It is concluded that layers of the chemically prepared material are approximately 10 times more porous than the electrochemically prepared films. High ionic conductivities previously obtained for polypyrrole/poly(styrene-4-sulfonate) layers bonded to Nafion membranes have been shown to be due to HNO3 generated in pores by ion exchange of residual Fe3+ with H+ in the Nafion.