The ways to strengthen oxide glasses are closely linked with surface defects, which act as stress amplifiers and thus reduce the practical strength of the material. In this chapter, a concise summary as to how to measure strength and stress limits are discussed in terms of advantages and drawbacks of the various methods. Furthermore, an overview is provided of the different ways to eliminate previously formed surface defects, including the different types of polishing and etching. Avoidance of surface defect formation is also discussed in terms of protective coatings as well as processing issues in the glass industry, such as cutting and finishing of glass products. Improvement of glass strength by inducing residual surface compressive stresses through thermal strengthening and different kinds of chemical strengthening is described. Finally, some applications through strengthening of oxide glasses and perspectives of the near future of thermal and chemical strengthening are provided.