The electrochemistry of methyl, ethyl and benzyl viologens was studied at polypyrrole doped with sulfonated cyclodextrin, PPys beta-CD, a cation exchange polymer. Three reduction waves were observed corresponding to the reduction of the viologen (V2+) to the radical cation (V+) followed by the neutral compound (V) and a third intense peak. This third reduction peak was associated with the ingress of V2+ as the PPysg.-CD film is reduced. As the incorporated V2+ is reduced to the neutral viologen, the influx of more V2+ occurs to achieve charge balance and this repeated influx and reduction of V2+ gives an intense reduction wave. These processes were only observed with s beta-CD as a dopant and this was attributed to the formation of an ion pair between the anionic cyclodextrin and the viologen. Lower diffusion coefficients and rate constants were observed for the reduction of V2+ and V+ on adding an excess of s beta-CD to the viologen solution. Linear calibration curves were obtained extending from 1.0 pM to 80 mu M when the PPys beta-CD was employed as a sensor for methyl viologen. While the PPys beta-CD is not suitable for the detection of low nM concentrations, the uptake and extraction of MV2+ was observed on polarising the PPys beta-CD in a solution of the viologen, highlighting the dual action of the polymer.