The dark electrical conductivity of Langmuir-Blodgett assemblies of phthalocyaninato-polysiloxane (PcPS) has been measured at room temperature as a function of the degree of electrochemical oxidation. The conductivity is observed to increase from <10(-6) S/cm for unoxidized PcPS to 10(-5) S/cm at an oxidation level of 20%, and to decrease upon further oxidation. The initial increase in conductivity upon oxidative doping is believed to arise from the introduction of charge carriers with mobilities of approximately 10(-6) cm(2)/Vs, while the subsequent decrease in conductivity at higher oxidation levels is attributed to reduced charge carrier mobility in the highly charged polymer.