We have studied the trigonal warping effect in metallic carbon nanotubes using resonance Raman scattering and examining the G'-band profile for individual metallic single-wall carbon nanotubes. We show that the observed splitting in the G'-band phonon spectra is directly correlated with the splitting in the singularities of the joint density of electronic states, i.e., detailed information about the 1D electronic structure is extracted from a phonon measurement. By correlating the phonon data with the calculated electronic structure for several (n, m) nanotubes, we were able to determine the G'-band dispersion [(partial derivativeomega(G')/partial derivativeE(laser)) = 108 +/- 6 cm(-1) /eV] by using a single laser energy. 2002 Published by Elsevier Science B.V.