Widely cited values of 89 and 90.9 kcal/mol for the bond-dissociation free energy of N-hydroxyphthalimide (NHPI) in water and acetonitrile, respectively, are in error. The sources of the errors leading to these values have been explored and corrected. The corrected values are confirmed through new experiments in aqueous and acetonitrile media and are found to be 84.4 ± 0.1 and 80.04 ± 0.06 kcal/mol, respectively.