The analysis of biomass tar by H-1 NMR, FT-IR, TOF-MS, GC-MS, and TG-MS indicated that it is different from tar or pitch from fossil fuels because of the remarkable oxygen content in biomass tar, originating from the botanical precursor, and it consists basically of phenols with one to three aromatic rings. It was polymerized in formaldehyde solution and yielded 70% of a tar-derived resin. The polymerization increased its molecular weights and improved its softening point. Although biomass tar gave a very small amount of char when carbonized at 600 degrees C, biomass resin exhibited twice the carbonization yield, about 30%. The resin was successfully spun, stabilized, and carbonized to carbon fibers at yields of 40-50%. The biomass resin-based carbon fibers showed mechanical properties (tensile strength and modulus up to 632 MPa and 44 GPa, respectively) comparable with commercially available samples. Further activation of carbon fibers provided activated carbon fibers with surface areas of 450-1600 m(2)/g, yields of 84-40%. The resin could also be spread over an aluminum foil, to be stabilized and carbonized into carbon films with thicknesses of 1-6 mu m. Such a resin can be expected to be a useful precursor to prepare carbon materials.