We investigated the electronic properties of the radial single-walled carbon nanotubes (SWCNTs) by using the Raman and the U'V-Vis-NIR spectroscopy. The radial SWCNTs for the analysis were synthesized by the arc-discharge method with Ce as a catalyst. The yield of the radial SWCNTs with 1.55 nm diameter and 60 nm length was as high as 20% in the soot. From the UV-Vis-NIR spectrum and the tangential mode of Raman spectra, the radial SWCNTs were confirmed to be composed of semiconducting (0.64 and 1.14 eV for V-s(1) --> C-s(1) and V-s(2) --> C-s(2)) and metallic (1.60 eV for V-m(1) --> C-m(1)) nanotubes. (C) 2004 Elsevier B.V. All rights reserved.