Micropatterning of organosilane self-assembled monolayers (SAMs) was demonstrated on the basis of photolithography using an excimer lamp radiating vacuum ultraviolet light of 172 nm. This lithography is generally applicable to micropatterning of organic thin films including alkyl and fluoroalkyl SAMs, since its patterning mechanism involves cleavage of C-C bonds in organic molecules and subsequent decomposition of the molecules. In this study, SAMs were prepared on Si substrates covered with native oxide by chemical vapor deposition in which an alkylsilane, that is, octadecyltrimethoxysilane, and a fluoroalkylsilane, that is, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, were used as precursors. Each of these SAMs was photoirradiated through a photomask placed on its surface. As confirmed by atomic force microscopy and X-ray photoelectron spectroscopy, the SAMs were decomposed and removed in the photoirradiated area while the masked areas remained undecomposed. Furthermore, these patterned SAMs served as masks for wet chemical etching in order to fabricate microstructures on their Si substrates. A micropattern 2 mu m in width was successfully transferred on the Si substrate with an edge resolution of 200 nm.