A black pi-conjugated azo polymer was synthesized by oxidative coupling of 3,5-diamino-1-octadecylbenzoate. The polymer, with a number average molecular weight of about 16 000, was soluble in chloroform. Monolayer formation was studied by transmission electron microscopy and the structure of the deposited Langmuir-Blodgett multilayer film was investigated with small angle X-ray diffraction and Fourier transform IR spectroscopy. A smooth monolayer was obtained when, after spreading, the material was allowed to disintegrate without any applied surface pressure for 18 h at 20-degrees-C and 1 h at 40-degrees-C. Monolayers could be transferred successfully onto different substrates at high temperature (40-degrees-C) and high pressure (30 mN m-1). The deposition was of the Y type with transfer ratios of 1 on both the downstroke and the upstroke. It was concluded that the aliphatic side chains are not able to crystallize and therefore form amorphous layers.