Variational transition state theory[1] is a refinement of transition state theory. When using transition state theory to estimate a chemical reaction rate, the dividing surface is taken to be a surface that intersects a first-order saddle point and is also perpendicular to the reaction coordinate in all other dimensions. When using variational transition state theory, the position of the dividing surface between reactant and product regions is variationally optimized to minimize the reaction rate. This minimizes the effects of recrossing, and gives a much more accurate result.