An atomic nucleus with a spin quantum number I > 1 2 possesses a nuclear quadrupole moment, which, when interacting with an external electric field gradient, gives the so-called quadrupole coupling. This coupling plays a dominating role for the relaxation rates of NMR signals of quadrupolar ions [1], but it can also give additional splittings of signals in systems, where the field gradient does not average to zero at the nuclear site. However, for a dilute aqueous solution of ions, the field gradient is caused by the surrounding water molecules, which, due to their motion, will average it to zero. Hence, there is no splitting, but the fluctuation of the field gradient will contribute to the relaxation. From the NMR experiment it is possible to estimate the product between the field gradient fluctuation, <V 2 zz> eq, and a correlation time τ c, associated with the motion of the water molecules. In this work we have focused our interest on the field gradient at the ion nuclear site, and the origin of it. Therefore, calculations with the Monte Carlo simulation technique have been performed on systems consisting of 50 water molecules surrounding an ion (Li +, Na + and Cl −). The configurations generated in the simulation have been used to calculate the field gradient fluctuations at the nuclear site of the ion. The results have been compared with experimental and other theoretical data. The analytical expressions for the intermolecular pair-potentials used in the Monte Carlo program, have been obtained from fitting of accurately calculated quantum mechanical (near Hartree-Fock) energies and field gradients of ca. 80 ion-water molecule confogurations. In Table I the calculated electric field gradient at the nuclear site of a lithium ion, and its fluctuation, I N <V zz> eq (a.u.) <V 2 zz> eq (a.u.) 4 2.2·10 −4 0.3·10 −4 5 2.9·10 −4 0.5·10 −4 10 −13.0·10 −4 1.·10 −4 50 23.0·10 −4 1.3·10 −4 exp. 0.14·10 −4 are shown. The experimental value is calculated with τ c = 10 −12 s. N is the number of water molecules, and the average are calculated from 200 000 configurations. The origin of the field gradient at the nuclear site has been discussed by several authors. Hertz [2] means that the dominating contribution to the field gradient comes from the water dipoles in the first hydration shell. Deverell [3], on the other hand, ascribes the distortion of the ionic electron cloud, when colliding with a water molecule, the largest contribution. By a detailed analysis of the configurations generated in the Monte Carlo procedure, we hope to bring some more light on the problem. So far the results indicate that the water molecules closest to the ion are far from the tetrahedrally arranged, thus giving a non-zero contribution to the field gradient at the nuclear site: They also seem to be quite mobile. These findings are in qualitative agreement with suggestions made by Friedman [4].