CVT/SCT is an extension to CTST that variationally optimizes the transition state location and includes multidimensional quantum effects on the reaction coordinate. Quantum effects on the reaction coordinate include both tunneling at energies below the effective barrier top and nonclassical reflection at energies above it, but both effects are incorporated in a factor that is simply called the tunneling transmission coefficient. CVT with a multidimensional tunneling transmission coefficient that includes corner-cutting tunneling has been shown to yield HAT reaction rates constants that agree well with accurate quantum dynamics (which are practical only for the simplest reactions). The success of CVT/MT depends on several important factors: a highly accurate PES, good choice of reaction coordinate (the reaction coordinate determines the dividing surface, since the latter is orthogonal to the former), an accurate treatment of vibrational anharmonicity, and a reliable way to estimate the tunneling contributions. In the present work, we use SCT as the choice of MT tunneling method. When used with high-quality potential energy surfaces (PESs), CVT/SCT often agrees well with experiment. Equating the reaction rate to the equilibrium flux through the transition state is only justified if the transition state is a dynamical bottleneck; otherwise, the rate constant is overestimated. Although the conventional transition state is located where the potential energy is a maximum along the minimum-energy reaction path, the location along the reaction path of the maximum in the free energy of activation may differ from the maximum of the potential energy. Because of the difference in these locations, free energies of activation obtained from a transition state passing through the highest potential energy along the reaction path will be lower than the true free energies of activation, and -if this were the only error -the rate constant would be overestimated. In CVT, this is ameliorated by replacing eq. 1 by 61,62