Recent experiments demonstrated lattice-oriented growth, controlled manipulation of carbon nanotubes and their nanoelectronic devices on surfaces. Using molecular dynamics simulation method and by performing electronic structure and electron transport calculations, we investigate nanotubes and their intermolecular junctions on surfaces. It is demonstrated that local atomic structure in nanotube-surface and nanotube-nanotube contacts plays important roles in friction and electronic transport at the nanoscale. Each nanotube has unique equilibrium orientations with respect to surface structure. Electronic transport is strongly enhanced when the atomic structures of the objects in contact are commensurate. (C) 2003 Elsevier Science B.V. All rights reserved.