Plasma polymerized N,N,3,5-tetramethylaniline (PPTMA) thin films were deposited on to glass substrates at room temperature by a capacitively coupled parallel plate reactor. The as-grown and heat-treated thin films of about 400 nm thick were characterized by infrared (IR) and ultraviolet-visible (UV-Vis) spectrometry. The structural analyses reveal that PPTMA thin films are formed with certain amount of conjugation, which modifies on heat treatment. From the UV-Vis absorption spectra, allowed direct transition (E-qd) and indirect transition (E-qi) energy gaps are determined to be 2.80 and 1.56 eV, respectively. While E-qd increases a little, E-qi decreases, on heat treatment of PPTMA. The calculated values of B for all the samples indicate an increase in structural order/conjugation in PPTMA thin films on heat treatment. (C) 2004 Published by Elsevier B.V.