The mechanical properties of a fiber-reinforced plastic are influenced by the adhesion between a reinforced fiber and a matrix resin. In this work it is shown how to obtain strong adhesion between a carbon yam and an epoxy resin through the formation of covalent bonds. Acid amide groups reactive with epoxy groups were introduced onto a surface of the yam by means of plasma-graft polymerization of acrylamide. The density of active radicals formed on a surface of the yam by the plasma irradiation was first increased with increasing discharge power and plasma irradiation time, and then the rates of the increase were largely decreased. The degree of grafting was linearly increased with increasing the surface density of active radicals. The yam embedded in diglycidyl ether of bisphenol-A/triethylenetetramine mixture was pulled out to obtain pull-out force after curing. Pull-out force was increased with increasing degree of grafting and the failure in pulling out of the yam was cohesive. The covalent bonds formed in the graft layer will result in an increment of pull-out force. (C) 2000 John Wiley & Sons, Inc.