We report on the electrochemical synthesis and direct observation of nanoscale photoluminescence (PL) of a single strand of poly(3-butylthiophene) (P3BT) nanowire. pi-conjugated P3BT nanowires having a diameter of similar to 200 nm were electrochemically synthesized by using 1-butyl-3-methylimidazolium hexafluorophosphate as a dopant, based on Al2O3 nanoporous template. From the UV and visible absorption spectra, the doping and dedoping effects of the P3BT nanowires, through the treatment of HF and NaOH solvents, were investigated. By means of a laser confocal microscope with a high spatial resolution, we clearly observed the variation of light-emitting color and PL intensity in the nanoscale for the single strand of P3BT nanowire with different doping states. (C) 2008 The Electrochemical Society.