The structural and electrical properties of the mixed monolayers and Langmuir-Blodgett (LB) films of BEDOTTF-C(10)TCNQ/arachidic acid were examined. The domain structure of the monolayer at the air-water interface was investigated by Brewster angle microscope. The results were in good agreement with the monolayer de conductivity behaviour. The conductivity of the LB films on the solid substrate was investigated as functions of the molar fraction of the complex and the layer number. LB films of more than five layers showed a percolation behaviour which is consistent with results reported previously K. Ogasawara, T. Ishiguro, S. Horiuchi, H. Yamochi, G. Saito, Y. Nogami, J. Phys. Chem. Solid 58 (1996) 39. The single- and bi-layer films were highly conducting when the molar fraction of the complex was high. The stability of these films with time was also examined.