Dopamine uptake and release was investigated with a quinone-containing conducting film, poly(5-amino-1,4-naphthoquinone) (PANQ), used for its intrinsic cation-exchange properties. The good electroactivity of this film in aqueous medium leads to interesting values of dopamine uptake, up to 100 nmol cm(-2) in a 300 nm thick film. The uptake and release mechanisms indicate a water counterflow during the doping process and competition with protons. The incorporated dopamine can be released by applying an oxidative potential, and such a film has possibilities as a dopamine vector for in vivo applications.