Molecular arrangement of two kinds of Langmuir-Blodgett monolayers composed of poly(N-dodecylacrylamide) and N-octadecylacrylamide win characterized with the atomic force microscope (AFM), The dodecyl side chains in the polymer Langmuir-Blodgett monolayer were observed as random molecular arrangement. In contrast, alkyl chains in N-octadecylacrylamide monomer Langmuir-Blodgett film were highly ordered to form two dimensional crystals. The X-ray diffraction patterns of the monomer and polymer Langmuir-Blodgett films were consistent with the AFM observation. The polymer Langmuir-Blodgett monolayer was not destroyed by AFM tip scanned in the contact mode, indicating that the monolayer is mechanically appreciably stable. (C) 1999 Published by Elsevier Science S.A. All rights reserved.