The dependence of the 13C, 15N, and 1H isotropic NMR chemical shifts on amine substitution of aromatic ring systems are examined both experimentally and by DFT/GIAO (density functional theory/gauge including atomic orbitals) methods. There are large, monotonic decreases in the chemical shifts at odd-numbered (ortho and para) pyrimidine ring positions which do not occur at the even-numbered (ipso and meta) atoms as amine groups progressively replace hydrogens at the latter positions. This behavior parallels the computed 2pz electron densities which for the pyrimidine series increase monotonically at N1, N3, and C5 but exhibit small changes at the C2, C4, and C6 positions. Identical trends are noted for the aminobenzenes. The ring atom chemical shifts and 2pz electron densities at ortho and para (but not meta) positions are quite sensitive to the orientations of the amine groups which are pyramidalized as the result of balance between delocalization with the ring and the use of strongly directed sp3 orbital...