Spintronics has become an increasingly important topic in device applications in the nanoscale. Several candidate systems have been studied both experimentally and theoretically in literature. In this work, we investigate the potential of Mn- and Cr-doped BN nanotubes as nanoscale devices in spintronics and magnetic applications using density functional theory. Our calculations indicate that Mn- and Cr-doped (8, 0) BN nanotubes display large magnetic moments (up to 4 mu(B)) and offer possibilities for spin-dependent transport. We also find that both Mn and Cr have large binding energies, which is important for ease of doping.