Catalyst reduction temperature was observed to affect the yield and diameter uniformity of carbon nanotubes (CNTs) produced on Co-Mo/ Al2O3 catalysts. The results show that on the whole, the reduced catalysts gave higher carbon yield. The CNTs obtained from the unreduced catalyst and the catalysts reduced at 400, 550, and 700 degrees C had diameters of 9.0 +/- 1.4, 11.0 +/- 1.8, 11.2 +/- 1.8, and 12.1 +/- 2.7 nm, respectively, showing that an increase in catalyst reduction temperature produced a slightly larger average diameter and wider diameter distribution. Raman spectra further elucidate that better-graphitized CNTs were produced on the catalysts reduced with increasing reduction temperatures. (C) 2007 Elsevier B.V. All rights reserved.