Recently, there has been much progress towards the establishment of SiO2 as a practical non-linear material. Three processes currently being explored for creating second-order nonlinearities in SiO2-based materials include: photoinduced second harmonic generation observed in fibers and fiber preforms, temperature/electric-field poling of bulk fused silica and of SiO2-based waveguide structures, and electron-beam irradiation of bulk lead silicate glasses. This paper reviews the current state of these three processes and discusses some advantages and disadvantages.