We report a controlled process to make carbon-nanotube tips for scanning probe microscopes. The process consists of three steps: (1) purification and alignment of carbon nanotubes using electrophoresis, (2) transfer of a single aligned nanotube onto a conventional Si tip under the view of a scanning electron microscope, and (3) attachment of the nanotube on the Si tip by carbon deposition. Nanotube tips fabricated using this procedure exhibit strong adhesion and are mechanically robust. Finally, the performance of these tips is demonstrated by imaging the fine structure of twinned deoxyribonucleic acid with tapping-mode atomic force microscopy in air. © 1999 American Institute of Physics.