One-dimensional structures, such as nanowires, nanorods and nanotubes, are being studied in an attempt to better understand the fundamental properties of nanostructure materials for a variety of applications.  A common synthesis method employed by numerous research groups are horizontal chemical vapor deposition (CVD) tube reactors in which solid, liquid and gas precursors are incorporated into a feed gas stream at elevated temperatures and reduced pressures.  Nanostructures synthesized in these tube reactors generally grow by the vapor liquid solid (VLS), vapor solid (VS) or metal-organic chemical vapor deposition (MOCVD) mechanism.  While catalyzing the growth of the nanostructures with well defined nanoparticles has resulted, in some cases, in narrow radial size distributions, the length of the structures can vary over 2-3 orders of magnitude.  To gain insight into the large length discrepancies, computation fluid dynamics (CFD) techniques were utilized to investigate temperature and mass gradients as well as the velocity field of a typical horizontal tube reactor with commonly used “boat” substrate holders for varying operating conditions. The simulation results show large temperature, mass and velocity gradients resulting in varying deposition rates as a function of axial position.  To alleviate undesirable temperature gradients, mass transfer limitations and detrimental stresses on the nanostructures during the growth phase, a one-of-a-kind CVD reactor has been designed and fabricated.  Subsequent CFD simulations show a significant enhancement in the consistency, with respect to axial position, of the deposition rate when compared to the standard horizontal system.  The prototype reactor is currently being used to repeat well-established syntheses, such as silicon and germanium nanowire growth.  The purpose is to investigate a possible enhancement over the control of variables such as length, crystal growth direction and compositional homogeneity.  Upon completion of the proof-of-principle experiments, the reactor will be incorporated into the design of new reactions for compounds such as EuO.