Density functional theory (DFT) and ab initic, multiconfigurational calculations have been performed to investigate the OH-toluene reaction. The applicability of DFT and ab initio theories to the OH-toluene reaction system is evaluated. The results reveal that the DFT method produces activation and reaction energies and rate constants of the OH-toluene reaction in good agreement with the experimental values. We predict the branching ratios of OH addition to ortho, para, meta, and ipso positions to be 0.52, 0.34, 0.11, and 0.03, respectively, significantly different from a recent theoretical study of the same reaction system. (C) 2002 Elsevier Science B.V. All rights reserved.