A series of PAN-based IM6 carbon fibers which were surface treated to different levels with a commercial method were pretreated with compounds representing the constituents encountered in epoxy matrices used in composites. This was done to pre-react any groups on the fiber surface with these compounds before composite fabrication in order to determine the effect of chemical bonding on fiber-matrix adhesion. The extent of chemical bonding was quantified using X-ray Photoelectron Spectroscopy (XPS). Chemical bonding between reactive groups in amine cured epoxy matrices and the surface groups present on these IM6 carbon fibers has been determined to be low (1_3%). Pre-reaction with the monofunctional epoxy compound (butyl glycidyl ether) eliminated the possibility of further reaction with the epoxy matrix and the fiber-matrix adhesion that was measured was the lowest value. Pre-reaction with the difunctional amine compound had no measurable effect on adhesion when compared to normal composite fabrication procedures. Pre-reaction with the difunctional epoxy compound however did increase adhesion levels over that attained without any pretreatment encountered in normal composite fabrication methods. These results showed that when compared to physical interactions between the fiber surface and the epoxy matrix alone, chemical bonding between the epoxy and the carbon fiber surface could increase the adhesion between fiber and matrix by about 34% while chemical bonding between the amino group and the carbon fiber surface can increase adhesion by about 18%. Quantitative measurements of the fiber surface microtopography were made with scanning tunneling microscopy. A systematic increase in the nanoscale topography (roughness) of the fiber surface was detected with increasing surface treatment. When quantified, it was concluded that surface roughness similarly accounted for a significant increase in fiber-matrix adhesion. Overall, it was concluded that the addition of the surface chemical groups that react with the matrix and are produced during surface treatment are added on a surface that is increasingly rougher. Both effects combine synergistically to increase fiber-matrix adhesion.