Carbon nanotubes (CNTs) are of great technical interest because of their high strength (~37 GPa), good electrical conductivity, excellent thermal conductivity (3 000 W m-1K-1), and good thermal stability at both low and high temperatures. A difficulty has been absence of reliable methods of controlling assembly of the large numbers of CNTs required for practical applications. We have developed, in collaboration with our partners at the NanoTech Institute, University of Texas at Dallas, a solid-state process for spinning CNTs into yarns without the use of binders that usually degrade the electrical and thermal conductivities. The singles yarns were twisted together to give coarser (multi-stranded) stronger yarns that were knitted using a miniature 5-needle machine. Mechanical and electrical properties of the yarns and knitted tubes were assessed simultaneously using specially developed test equipment. Some specific applications under investigation include using the CNT yarns as incandescent and x-ray filaments, as electrodes for biomedical applications, and as composites with high toughness. Tests show the biocompatibility of the CNT yarns for selected cell lines is high.