The first aim here was to replicate an earlier study 9 reporting calculated kinetic isotope effects for the key hydrogen transfer step in the Swern oxidation of an alcohol to an aldehyde. conducted some 13 years ago using an earlier version of the Gaussian program. For the gas phase model, the replication was essentially exact. The task proved more complex when a continuum solvation model was included. Although the latest version G16 has keywords that aim to reproduce the solvation model and other parameters used in the earlier version G03 of the program, using this approach resulted in significant energy gradients when the original geometry was tested. There were also uncertainties relating to the transition state coordinates deposited as part of the original modelling of kinetic isotope effects, 9 and whether they related to their optimisation in a gas phase or solvent-continuum environment. Because no original vibrational analysis was included in the supporting information, we had to reoptimise these geometries to obtain the essential input into the Bigeleisen-Mayer equations used to predict the kinetic isotope effects (KIE). This replication was less accurate, but did not alter the original conclusion that the values of the isotope effects were predicted to be significant smaller than those experimentally measured -a result that was described as being a significant deviation from transition state theory for this reaction.