Abstract: At least partially carbonized fibers formed by pyrolysis from precursor fibers are converted to graphitic fibers in successive heating and stretching zones in which a transitional phase of high fiber reactivity is utilized. Chemical agents applied to the fibers during this transition increase matrix-fiber adhesion properties by reacting with the fibers before they develop excessive levels of crystallographic order and become inert at graphitization temperature levels. Improved control of fiber properties is achieved by employment of short residence times and resistive heating with concurrent stretching in the zones, and by imparting high stretch levels at relatively low temperatures to the fibers. The resultant fibers have superior properties for component structures and at the same time have excellent tenacity and modulus values as well.