Integrated optic devices are normally confined to within a few microns of the surface. This is the depth scale which is readily accessible to ion implantation techniques. Optical waveguides and associated components may thus be written directly into a substrate or thin film by a combination of masking and ion implantation. The earlier development of implantation for semiconductors has been extremely successful and liberated circuit design from the constraints of diffusion controlled circuits and allowed high tolerance, high density inte-grated circuits to be formed. For optical systems similar advantages allow refractive index depth profiling, strong lateral confinement of low loss waveguides and spatial variation of electro-optic and SAW properties. A full exploitation of the implantation techniques to thin film systems has still to be made. This paper will give examples of current progress in ion implanted waveguides and electro-optic devices with materials ranging from silica and lithium niobate to gallium arsenide. These will demonstrate the mechanisms by which the refractive index or optical properties can be controlled. Related ion implantation effects will be briefly mentioned.