The geometries and electronic structures of free-base porphine (P) and a number of centrosymmetric metalloporphines (RI-P) have been calculated by using density functional theory (DFT). The polarizabilities and second-order hyperpolarizabilities (gamma) of these porphines were calculated at the DFT level. The DFT calculations predict gamma to have the order P similar to Ni-P < Mg-P < Pd-P < Zn-P < Ca-P < Fe-P < Cd-P < Ru-P. The calculated value for gamma is larger for metals having 2, 8, and 12 valence electrons as compared to those with 10 valence electrons. The origin of the differences in the values of gamma is discussed in terms of the changes induced by the metal.