Electro-optic polymers have emerged as an interesting class of nonlinear optical materials suitable for application in broad band optical signal transmission. They take advantage of excellent propagation properties of amorphous polymer matrix with large nonlinear optical response of embedded chromophores. Different, important from practical point of view, aspects of material elaboration and chromophore orientation as well as its temporal stability are reviewed and discussed. A special attention is paid to the recently discovered problems of relaxation of nonlinear optical susceptibility due to the chromophores diffusion and aggregation, particularly important in the guest host systems.