Carbon nanotubes (CNTs) were synthesized through raw-material evaporation and condensation in RF thermal plasmas to investigate co-condensation process of the vapor mixture of carbon and metals. Addition of 10 wt.%-Ni was the most effective for the CNT synthesis, while Co, Fe, Mo, LaB6 had poor activity. These metal combinations presented synergy effect for the CNT formation. The combinations of Ni-Co, Ni-Fe, and Ni-LaB6 provided more effective activity in the CNT synthesis. Furthermore, the CNT growth mechanism from the vapor mixture of carbon and metals was discussed. Heterogeneous condensation model and carbon-metal molten model were selected as the CNT growth model. (c) 2005 Elsevier B.V. All rights reserved.