Compositions comprising high levels of high specific activity copper-64, and process for preparing said compositions. The compositions comprise from about 2 Ci to about 15 Ci of copper-64 and have specific activities up to about 3800 mCi copper-64 per microgram of copper. The processes for preparing said compositions comprise bombarding a nickel-64 target with a low energy, high current proton beam, and purifying the copper-64 from other metals by a process comprising ion exchange chromatography or a process comprising a combination of extraction chromatography and ion exchange chromatography.