We synthesized an optically active regioregular poly(3-substituted thiophene), head-to-tail poly(3-[2-((S)-2-methylbutoxy)ethyl] thiophene) (HT-P(S)MBET), according to a modified Rieke method. The HT-P(S)MBET was an optically active polymer with the HT linkage of larger than 93%, as estimated by NMR. The mixed monolayers of the polymer and stearic acid (SA) were found to be stable at the air-water interface and could be deposited onto solid substrates as Y-type films by the vertical dipping method. These Langmuir-Blodgett (LB) films exhibited well-defined layer structures and unique optical properties. The electrical conductivities of the LB films with and without doping of SbCl5 were about 10(-1) and 10(-5) S/cm, respectively.