Accurate equilibrium geometries, harmonic vibrational frequencies, and equilibrium rotational constants of the methyl radical were computed using coupled-cluster theory in combination with the cc-pVnZ and cc-pCVnZ basis sets of Dunning. Valence and all electron calculations were carried out. Using all electron correlations and CBS extrapolation, the re value is equal to 1.0758 Å, which is 0.0032 Å shorter than the experimental value of r0 (1.079 Å). The harmonic (ω1, ω2, ω3, and ω4) frequencies calculated using the CBS extrapolation differ from the experimental fundamental frequencies, respectively, by +142, +125, +21, and –82 cm-1. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]