We have produced the first macroscopic objects comprised of highly aligned single-wall carbon nanotubes (SWNTs). These objects are thin membranes prepared by producing a suspension of SWNT segments. introducing the suspension to a strong magnetic field to align the segments, and filtering the suspension in the magnetic field to produce an aligned membrane of SWNT. These membranes exhibited natural cleavage planes parallel to the magnetic field. This preparation of macroscopic samples of aligned single-wall nanotubes permits exploitation of their highly anisotropic properties, and will enable measurement of the electronic, thermal. magnetic, mechanical, and optical properties of bulk nanotube materials.