Coatings for plastic optics fall into two major categories in today's marketplace. One is in the opthalmic or eyeglass market, the other is precision optical instruments for industrial or military use. It is in the latter area we will concentrate this paper. The most common plastics used for these purposes are polycarbonates, polymethyl methacrylate and allyl diglycol carbonate (CR-39). They are normally made by casting or injection molding processes. Each of these materials have distinctive properties from one another but share other properties in common. We will discuss problems associated with organic substrates in general, some of the pros and cons of the three materials mentioned in relation to thin film coatings, solutions in dealing with these problems, and finally, examples of coated optics.