A stable monolayer of N-octadecylaniline containing stearic acid at the air-water interface has been obtained. However, the Langmuir monolayer of pure poly(N-octadecyl aniline) was not stable, but mixed Langmuir-Blodgett films of this polymer with stearic acid in different ratios as a spreading aid were stable. The electrical conductivity of these films increased by five orders of magnitude after doping with iodine as compared to that before iodine doping (5.8 x 10(-7) S cm(-1)). Temperature-dependent electrical conductivity suggested that these films were semiconducting in nature with low thermal activation energy. Impedance analyses of these films revealed that the equivalent circuit for poly(N-octadecylaniline) was (RQ) whereas that for mixed poly(N-octadecylaniline) with stearic acid was (RQ)(RQ). (c) 2004 Elsevier Inc. All rights reserved.