The wide use of polymer composites in structural applications has created a need for a deeper understanding of their micromechanical behavior. More importantly, it is essential to correlate the composite micromechanical behavior with their macromechanical behavior under different service conditions. For the last three decades, interfacial micromechanics and environmental durability of polymer composites have been investigated but a number of questions remain regarding the mechanism of interfacial degradation. The recent application of micro-Raman spectroscopy (MRS) in the field of composites micromechanics has created a new era of experimental micromechanics and shed light on a number of crucial points. This paper summarizes an MRS study of interfacialdegradation and the degradation mechanism in graphite/epoxy composites. Degradation behavior was studied in single fiber, multi fiber and bulk composites. The data consistently show a mechanical degradation mechanism in high modulus fiber / Epon 828 MPDA cured matrix composites.