We report a novel switching method that occurs due to the electro-optic effect under applied field when a beam incident on an interface between anti-parallel domains in a sample of LiNbO 3 subtends an angle greater than that required for total internal reflection (TIR). We present data obtained for wavelengths of 0.543 and 1.52 μm and compare this with a theoretical model. This switch has many attractive properties, as TIR is a 100% efficient process leading to the possibility of high contrast ratios; current data shows contrast ratios greater than 100:1 (20 dB). Other properties include relatively simple fabrication procedure, low drive voltages and a wavelength dependence that is less than other electro-optic devices such as Pockels cells.