The title of my talk is somewhat misleading in that if you expect to hear about new exciting non-linear materials of proven quality then you will, I fear, be disappointed. Having searched the literature for many months and having attended many conferences in the past year, I am forced to come to the conclusion there are very few, if any, new exciting non-linear materials on the scene. In fact I think its true to say that there are only two materials which seem to be reliable, and even these are to some extent suspect. All is not gloomy, however, and during the course of this talk I will have occasion to mention a few new materials and discuss some of their properties. Before we discuss specific materials I think it would be worthwhile to review briefly the subject of non-linear optics and to discuss some of the uses of the non-linear materials. In particular I would like to discuss what qualities are required of them before they are declared useful.