A new polymer has been prepared by anodic polymerisation of N,N'-diamino-4,4'-bipyridilium as the tetrafluoroborate salt in aqueous acidic at a gold electrode. The polymer was electroactive and conductive, with (D) over bar for the inserting counter ion being 8.0 x 10(-10) cm(-2) s(-1) during reduction and 4.8 x 10(-10) cm(-2) s(-1) during oxidation. The polymer was not electrochromic, being blue-black at all impressed potentials. Yields of polymer were poor, being particularly so at low pH (0 < pH < 1). The best pH for electrodeposition was about 2.0. N,N'-diamino-4,4'-bipyridilium was not electroactive at negative potentials. Conversely, N-aminopyridinium yields a blue water-soluble radical on reduction, and electron transfer to N,N'-bis(4-aminophenyl)-4,4'-bipyridilium as the dichloride salt-which has a particularly stable radical cation-yields a thin film of red-black radical-cation salt. Neither of these two latter species are electroactive at positive potentials.