We have grown singlewalled carbon nanotubes (SWNTs) over MgO-supported Ni catalyst particles at 800 degreesC with a mixture of acetylene and hydrogen gases. The diameters of SWNTs grown on 3 wt% Ni-MgO particles ranged from 0.7 to 1.0 nm, having a narrow diameter distribution compared to the previous works. This was attributed to the preparation procedure of Ni-MgO templates. Ni catalyst was co-precipitated with MgO, where an appropriate amount of Ni catalyst with uniform grain size remained on MgO surface after forming a solid solution during reaction. This method should be useful for a selective growth that is applicable to future electronic devices. (C) 2003 Elsevier B.V. All rights reserved.