The interlaminar interface in carbon fiber (continuous) epoxy-matrix composites was studied by measuring the contact electrical resistivity of this interface. The contact resistivity was found to decrease with increasing curing pressure and to be higher for unidirectional than crossply composites. The lower the contact resistivity, the greater was the extent of direct contact between fibers of adjacent laminae. The activation energy for electrical conduction in the through-thickness direction was found to increase with increasing curing pressure and to be lower for unidirectional than crossply composites. The higher the activation energy, the greater the residual interlaminar stress.