This article critically surveys spectroscopic data for the two lowest states (X (1)Sigma(+) and a (3)Sigma(+)) of NaK. These states both dissociate to ground state Na and K atoms. Since both states are known precisely to near dissociation, they can be used to determine experimental values of the separate Coulombic and exchange contributions to the long-range interaction potentials, which agree reasonably well with theory. We also discuss the dissociation energy of both of the states and recommend D-e(X (1)Sigma(+))=5273.65 +/- 0.10 cm(-1) and D-e(a (3)Sigma(+))=207.79 +/- 0.10 cm(-1).