Computed association energies and dissected nucleus-independent chemical shifts (NICS) document the mutual enhancement (or reduction) of intermolecular interactions and the aromaticity of H-bonded substrates. H-bonding interactions that increase cyclic 4n + 2 pi-electron delocalization boost aromaticity. Conversely, such interactions are weakened when aromaticity is decreased as a result of more localized quinoidal pi character. Representative examples of the tautomeric equilibria of pi-conjugated heterocyclic compounds in protic solvents and other H-bonding environments also illustrate such H-bonding/aromaticity interplay.