Ab initio HF/6-31G* electrostatic potentials and average local ionization energies have been computed for 42 nitrogen, oxygen, and sulfur bases. The molecules are characterized by four computed quantities, V-min, the spatial minimum in the electrostatic potential, PVmin, a polarization correction to V-min, <(I)over bar(S,min)>, the surface minimum in the average local ionization energy, and II, a global index derived from the calculated surface electrostatic potential. It is shown that shifts in the O-H stretching frequencies for methanol-base complexes, complexation enthalpies for phenol-base and iodine-base interactions, and gas phase protonation enthalpies can be well correlated to the computed quantities of the bases by a single type of relationship. An analysis of the importance of the different quantities for correlating a specific interaction provides information about the nature of the interaction.