When the energy of α-particles emitted by radioactive nuclei is compared with the energy calculated from the usual semi-empirical formula for nuclear binding energies, systematic variations ranging from 4.5 MeV. to -1.0 MeV. are found, which exhibit in a very clear way the special importance of configurations containing 82 protons and/or 126 neutrons. The general features are readily explained in terms of the shell model. The analysis can be used to predict unknown α-energies. Calculated α-energies are tabulated for the heavy nuclei (Z ≥ 78) and for nuclei in the rare-earth region.