Abstract Rheo-optical FTi.r. spectroscopy was used to study molecular orientation phenomena in highly crosslinked epoxies on the basis of the diglycidyl ether of bisphenol-A and a polyetherdiamine. In previous publications, their orientation behaviour during continuous uniaxial deformation was described. The present paper reports on the rheo-optical characterization of these resins during specific cyclic deformation experiments below the glass transition temperature ( T g). Epoxy films were subject to various successive loading—unloading cycles including elongation, recovery, annealing, and stress relaxation in order to study the reversibility of the orientation during relaxation processes. The investigations show that the orientation is only in part reversible upon unloading or stress relaxation below T g. However, it can be annealed by heating the epoxy resin to above T g. Furthermore, it was found that no significant fatigue due to chain scission occurs until failure of the sample. The results were discussed with respect to the mechanism of plastic deformation.