At the present level of electronic-structure theory, the differences between calculated and experimental indirect nuclear spin-spin coupling constants are typically as large as the vibrational contributions to these constants. For a meaningful comparison with experiment, it is therefore necessary to include vibrational corrections in the calculated spin-spin coupling constants. In the present paper, such corrections have been calculated for a number of small molecular systems by using hybrid density-functional theory (DFT), yielding results in good agreement with previous wave-function calculations. A set of empirical equilibrium spin-spin coupling constants has been compiled from the experimentally observed constants and the calculated vibrational corrections. A comparison of these empirical constants with calculations suggests that the restricted-active-space self-consistent field method is the best approach for calculating the indirect spin-spin coupling constants of small molecules, and that the second-order polarization propagator approach and DFT are similar in performance. To illustrate the usefulness of the presented method, the vibrational corrections to the indirect spin-spin coupling constants of the benzene molecule have been calculated. (C) 2003 American Institute of Physics.