This work aims to investigate the electrical conductivity sensitivity of polydiphenylamine (PDPA) pellets, films, and fibers when they are exposed to methanol vapor. PDPA was synthesized via chemical oxidative polymerization and washed with NH4OH solution to obtain the de-doped-PDPA (De-PDPA). De-PDPA pellets were doped with hydrochloric acid at various doping ratios. PDPA and its blends with polyethylene oxide (PEO) added at various ratios were successfully fabricated into fibers by electrospinning and cast into films. The De-PDPA pellet doped at the doping ratio of 100 has the highest electrical conducitivity sensitivity toward methanol vapor. The electrical conductivity sensitivity of the PDPA electrospun fiber is relatively lower than those of the D-PDPA cast films under methanol vapor. The methanol vapor induces a higher degree of crystallinity in the conductive polymer matrix and resultant higher electron mobility. The adsorption of methanol vapors is investigated via FTIR and the interaction is irreversible. (C) 2011 Wiley Periodicals, Inc. Adv Polym Techn 31: 401413, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.20263