Ab initio configuration interaction (CI) calculations were performed on the ground and excited state of Hf@C-28 and its positive and negative ions. Relativistic core potentials, spin-orbit operators, and symmetry-adapted functions were included in the calculations to take into account the relativistic effects of the heavy atom and to reduce the time and effort of the computation. Double-zeta basis sets were used. Single and double excitations were included in the CI calculations. A number of excitation energies were obtained for Hf@C-28 and its ions. The ground states of Hf@C-28(+), Hf@C-28, and Hf@C-28(-) in T-d symmetry were found to be (2)A(1), (1)A(1), and (2)E. For Hf@C-28, values found were the following : ionization potential, 8.08 eV; electron affinity, 0.66 eV; and first excitation energy (to (3)E state), 5.26 eV. The binding energy for Hf and C-28 to form Hf@C-28 was obtained as 0.71 eV. These results were compared with those from our previous SCF calculations and with experimental data or other theoretical values where available.