Nanotube and nanobamboo structures of boron nitride (BN) have been synthesized by heating a mixture of boron and iron oxide in flowing ammonia gas. The reaction temperature and the ratio of B/Fe2O3 are found to play an important role in determining the diameter and morphology of the product. The in situ generated nanoscale iron catalysts are responsible for the nanotube-like growth. The growth of BN nanotube and nanobamboo structure is ascribed to a catalytic growth within the framework of a vapor-liquid-solid catalytic growth mechanism.