The Langmuir-Blodgett films of terthiophene-vinylbenzoate (TSe) embedded in an octadecyl amine (ODA) inactive matrix were found to maintain an ordered head-to-tail (Z-type) structure up to at least 20 molecular layers. UV-Vis polarized absorption and polarized second-harmonic generation indicate that TSe is oriented in the films with the molecular axis aligned about the film normal. The degree of orientation increases for thick films suggesting that the ordering of the first few layers is compromised by substrate roughness. Improved orientation is obtained also by depositing pure ODA layers before the active layers. (C) 2003 Elsevier B.V. All rights reserved.