The optical transmittance spectra of polypyrrole perchlorate have been measured at various stages in the reduction to neutral polypyrrole at 300 and 120 K and at high pressure. Analysis of the results suggests that the polypyrrole chain is composed of conjugated segments of various lengths. The optical conductivity spectrum of polypyrrole perchlorate was obtained by the Kramers-Kronig transformation of the transmittance data from 0.025 to 6.25 eV. The spectrum is not consistent with Drude-like free carriers. The conduction mechanism probably involves hopping between the conjugated segments. © 1983 American Institute of Physics.