An integrated optical switch based on liquid crystal on silicon is reported. The switch consists of an optical waveguide, whose core is made of nematic liquid crystal E7 infiltrated in a SiO 2 /Si V-groove. The electrooptic effect allows us to control the waveguide propagation condition by means of ITO and Si electrodes. A voltage as low as 2 V applied to the driving electrodes turns the waveguide on. Since the output intensity increases with voltage, the waveguide behaves also as a variable optical attenuator. A maximum ON-OFF extinction ratio in excess of 44 dB was measured.