Formation of the supported planar bilayer of dipalmitoylphosphatidylcholine (DPPC) on SiO2 surfaces modified with the self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) has been investigated by atomic force microscopy (AFM). DPPC was deposited by the fusion of vesicles on SiO2 surfaces with OTS-SAM islands of different sizes and densities. The DPPC bilayer membrane formed self-organizingly on the SiO2 surface with small and sparse OTS islands, while did not when the OTS islands were larger and denser. The relative size between the vesicles and the SiO2 regions is the critical factor for the formation of the DPPC bilayer membrane. (C) 2004 Elsevier B.V. All rights reserved.