In the course of development of any new technology the issues of device stability and reliability are inevitably encountered and must be summarily dealt with. The development of organic and polymeric nonlinear optical media has been no exception and has now evolved to a stage wherein solutions to a few performance issues are of crucial importance. Discussions here focus on just two of these critical problems. First, we describe a preliminary study intended to identify some of the variables involved in optical damage. The goal here is to identify suitable photochemically stable chromophores and polymers and to elucidate any processing and environmental influences which contribute to damage. Second, the thermal stability of nonlinear optical chromophores has already attracted much attention and significant progress has been made in enhancing the thermal stability of many systems. Our most recent effort has concentrated on chromophores with a variety of different configurations and combinations of nitrile acceptor groups, some of which possess both large nonlinearities and excellent thermal stability. Some newer aspects of a thermal stability screening protocol which are particularly useful for these thermally stable chromophores and polymers are also described.