Phonon modes of single-walled carbon nanotubes were observed by means of hyper-Raman scattering. The infrared active G- and D-bands were clearly observed in the spectrum, while no infrared-inactive radial breathing modes were detected. Both one- and two-photon electronic resonances were found to contribute to the scattering intensity enhancement, which suggested the possible utility of hyper-Raman spectroscopy as a unique tool for detection of vibrational modes. (c) 2007 Elsevier B.V. All rights reserved.