This paper presents measurements of the principal values of the N-15 chemical shift tensors in adenine, cytosine, guanine, and thymine. The assignment of the solid-state NMR resonances was done using the liquid values in the corresponding nuclesides and the results of quantum mechanical calculations of the N-15 tensors, The calculations were also used to assign the orientation of the principal axes of the tensors and to evaluate the effect of intermolecular interactions on the N-15 chemical shift tensors of the nucleic acid bases. The results indicate that calculations including intermolecular interactions produce results in better agreement with the experimental values than those in which these interactions are neglected.