The formation of epitaxial nanotubes (nanoarches) on the surface of hexagonal BN (h-BN) during electron irradiation is reported. In addition to implications in terms of understanding fullerene based structures, we suggest that these act as the nucleation sites for cubic BN (c-BN) growth and may lead to improved film growth. We also report a strong dependence upon the microscope vacuum, which may be critical in understanding irreproducibility in film growth. ©1998 American Institute of Physics.