Fascination with carbon-based nanotubes is leading to a range of advanced nanocomposites, but not without the developed understanding of how to manipulate the nanotubes for property development. A better understanding of carbon nanotube based nanocomposites can be derived from a matrix of understanding when studying nanotube insertion into a variety of matrices. The general methods to advance carbon nanotube based nanocomposites involves consideration of nanotube starting conditions, dispersion, interaction with the matrices, and alignment. Generally, where advancement has been achieved, nanotube functionalization has been a key contributor either to advance dispersion or to provide fuller linkage to the matrix. Interesting cases have emerged where advanced properties have been seen for entangled nanotube and polymers, as in the case of elastomers, and for forests of nanotubes, as in the case of macroscale fiber systems with well-grown nanotubes on the fibers. In this chapter, the role of nanotubes in nanocomposites will be considered as to property development. While most groups have considered low-concentration systems, there are still opportunities for more research and advanced properties from high-concentration systems. The fuller use of carbon nanotubes may well rest with more self-assembly and synergistic behavior between nanotubes and other nanospecies.