Carbon nanofibers were catalytically grown by the decomposition of C2H2/H-2 over an unsupported Ni catalyst. The aim of this article is to study the main and interaction effects of temperature (500-600 degrees C). H-2 flow rate (0-100 ml/min), and C2H2 flow rate (100-200 ml/min) on the yield and properties of carbon nanofibers. Full 2(3) factorial designs with three replicates at the center point and thus a total of 11 experiments were carried out. It turns out that when temperature increases there was a significant increase in the yield, in the BET, and also in the pore volume of the carbon nanofibers. On the other hand, increasing H-2 flow rate decreases the yield, the BET, and also decreases the pore volume of carbon nanofibers. Increasing C2H2 flow rate has an insignificant effect on the yield and it decreases the BET surface area and pore volume. The work shows that not only the effects of the main parameters are important, but also the interaction effects between them are significant. The study helps optimizing the process of carbon nanofibers growth. (C) 2009 Elsevier B.V. All rights reserved.