The present study describes a new method for obtaining a more accurate transition state estimate through interpolation of the reaction pathway. The method can be implemented using the reaction pathway or during the reparameterization step of the modified-growing string method. The transition state estimate is obtained by mapping the location of the maximum in energy along the reaction pathway to a set of coordinates in phase space. This method has been tested on three reactions of increasing complexity, representing a 35.0-77.8% reduction in CPU time for the transition state optimization calculation compared to using the geometry highest in energy. (C) 2009 Elsevier B.V. All rights reserved.