This chapter discusses the properties and interactions of atomic defects in copper (Cu). Copper is one of the classical model substances for the investigation of radiation damage and the resistivity annealing have been investigated after irradiation with electrons, protons, thermal neutrons and fast neutrons. The amount of the low temperature annealing depends on the irradiation dose for e--irradiation and to a much smaller extend for cascade damage. The annealing after quenching is illustrated. Similarly the annealing after low temperature plastic deformation is systematically investigated. Properties of Frenkel pairs, self-interstitial atoms and vacancies in pure copper are tabulated. The influence of plastic deformation on the defect production by neutron irradiation and the annealing has been investigated and MechR (dislocation pinning) has been used for the investigation of the interaction of defects with dislocations. Interstitial solute interaction has been extensively investigated by resistivity annealing and damage rate measurement and these results have been reviewed recently. Additional information has been obtained from MechR and PAC. Characteristic for Cu are several annealing peaks within the range of annealing stage II and finally complete annealing of the excess resistivity compared to the pure Cu. This final annealing step has often been attributed to dissociation of the SIA-SA complex, and corresponding binding energies have been determined. The information on vacancy-SA complexes are tabulated. The data are mostly based on ΔQ and PAS experiments. Most detailed information on trapped single, di- and tri-vacancy complexes has been obtained for the nuclear probe atom In.