Surface properties of polycarbazole at air-water interface have been investigated for the first time by measuring pressure-area isotherms. Pure polycarbazole films have been deposited successfully on different substrates by Langmuir-Blodgett technique using a mixture of dimethylsulfoxide and chloroform as spreading solution. Polycarbazole monolayers were found to remain stable on the water sub-phase. It has been observed that area per carbazole molecule for these layers did not change significantly with change in sub-phase pH. In order to make a comparative study, films were also deposited from polycarbazole mixed with octadecyl amine (ODA), using different feed ratios of polycarbazole and ODA. Deposited films of pure and ODA-mixed polycarbazole were characterized by electrochemical methods, UV-Visible (UV-Vis) spectroscopy and atomic force microscopy (AFM). UV-Vis spectroscopy confirmed the layer by layer formation of polycarbazole Langmuir-Blodgett (LB) films. Cyclic voltammograms of pure polycarbazole LB indicated their organiz d s c re. AFM study on both kinds of LB films showed globular structure. These polycarbazole LB films were also studied for their potential for sensing ammonia gas. (c) 2005 Elsevier B.V. All rights reserved.