Femtosecond laserpatterning of octadecylsiloxane monolayers on quartzglass at λ=800nm, τ<30fs, and ambient conditions has been investigated. Selective decomposition of the coating with single laser pulses at subwavelength resolution can be carried out over a wide range of fluences from 4.2 down to 3.1J/cm2. In particular, at a 1/e laser spot diameter of 1.8μm, structures with a width down to 250nm and below were fabricated. This opens up a facile route towards laser fabrication of transparent templates with chemical structures down into the sub-100-nm-regime.