Laser direct processing of glass has been challenging due to the brittle nature and poor heat transfer characteristics of the material. With the advancement of ultrashort pulse lasers, laser direct machining of glass with smooth surface and free of microcracks has become a potential manufacturing technique in microfabrication of optical devices. In this paper, machining of microgrooves on fused silica substrates using a p-polarised femtosecond laser beam was investigated with regards to the groove profile and surface morphology. Microchannels with width and spacing of 20 pm were produced with no microcracks. Repeatable sub-micron gratings within a microchannel along the cutting direction were also observed. These microchannels and gratings may be used for the manufacture of optical and microfluidic devices. The beam polarisation was found to have little effect on the machining results. (C) 2004 Elsevier B.V. All rights reserved.