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 wavelength. This lithography is generally applicable to micropatterning of organic thin films including alkylsilane 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 [CH3(CH2)(17)Si(OCH3)(3), ODS] was used as a precursor. SAM was photoirradiated through a photomask placed on its surface so that it was decomposed and removed in the photoirradiated area while the masked areas remained undecomposed. Accordingly, the photomask image was printed on the SAM as a removed/unremoved pattern. The patterned SAM could be used as a mask for plasma etching or area-selective Ni electroless plating.