Conductive Langmuir-Blodgett (LB) films were fabricated from mixed monolayers containing structurally homogeneous poly(3-hexyl-thiophene) and stearic acid in different molar ratios. The structure of these mixed LB films was probed by visible absorption and X-ray diffraction measurements. These regioregular polymers containing almost 100% head-to-tail couplings showed the self-organized properties and affected the molecular structure in the LB films. Conductivities of the LB films doped with strong oxidizing agents were dramatically improved due to their well-defined polymer structure and were in the range of 10(2)-10(1) S cm(-1).