TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The method further involves carbonizing the stabilized polymer fiber under tension in an inert environment, at 500-1800 degrees C for 2 hours or less, and graphitizing the carbonized polymer fiber under tension in a non-nitrogen-containing inert environment at 1800-2800 degrees C for 1 hour or less. The drawn polymer fiber is stabilized under tension in an oxidizing environment, at 200-400 degrees C for 36 hours or less. The method alternately involves contacting carbon nanotubes (CNT) with acrylonitrile-containing polymer, gel-extruding the polymer-CNT dope, drawing the polymer-CNT fiber precursor, stabilizing the drawn polymer-CNT fiber, to form stabilized polymer-CNT fiber, carbonizing the stabilized polymer-CNT fiber, and graphitizing the carbonized polymer-CNT fiber, and/or contacting graphite sheets with acrylonitrile-containing polymer, gel-extruding the polymer-graphite sheet dope to form a polymer-graphite sheet fiber precursor, drawing the polymer-graphite sheet fiber precursor, stabilizing the drawn polymer-graphite sheet fiber, carbonizing the stabilized polymer-graphite sheet fiber, and graphitizing the carbonized polymer-graphite sheet fiber. Preferred Component: The carbon nanotube (CNT) comprises single wall nanotube, double wall nanotube, or triple wall nanotube. Preferred Properties: The drawn polymer fiber has average diameter of 100 nm-100 mu m. The carbon fiber has average cross-sectional dimension of 50 nm-50 mu m. The carbon nanotube has average diameter of 0.5-100 nm, alternately 10 nm or less, and average length of 10 nm or more. The drawn polymer-CNT fiber has average diameter of 100 nm-100 mu m. The carbon fiber has electroconductivity of 25% or more, higher than that of carbon fiber comprising no carbon nanotubes. A drawn polymer-CNT film formed using carbon fiber has average thickness of 50 nm-500 mu m. The carbon fiber or carbon film has tensile strength of 0.5 GPa or more, preferably 0.7 GPa or more, and more preferably 1.2 GPa or more, and tensile modulus of 50 GPa or more, preferably 77 GPa or more, and more preferably 148 GPa or more, higher than the carbon fiber or carbon film produced without CNT. The carbon fiber or carbon film has tensile strength of 0.5 GPa or more, and tensile modulus of 50 GPa or more, higher than the carbon fiber or carbon film formed without graphite sheets. The carbon fiber or film is optically transparent. Preferred Composition: The carbon nanotube comprises dope (0.001-80 weight%) and carbon fiber (0.001-80 weight%). The carqfbon nanotube in the carbon fiber is exfoliated. The carbon fiber comprises a crystallized graphitic region radially extending to 0.34-50 nm, alternately 2 nm or more, from a wall of each CNT. The polymer-CNT dope comprises 1 wt.% or more of carbon nanotube with respect to weight of acrylonitrile-containing polymer.