In this paper we review and discuss the effect of light illumination and of heating on polar order in electro-optic polymers and its practical implications. Both have a positive and negative influence. Light may create polar order but destroy it too. Similarly the heating increase the polar order by increasing the chromophore mobility, but in the same time it destroys it due to the increased chromophore diffusion. The mechanisms connected with these phenomena are presented and discussed. (c) 2007 Elsevier B.V. All rights reserved.