The radionuclides currently used for cancer therapy are reviewed. The radionuclides involved are the pure β emitters

the β emitters with accompanying γ-ray emission suitable for imaging as well as the internal conversion electron and Auger electron emitters. The problems related to the production of these radionuclides in nuclear reactors are discussed. It is indicated that the spallation neutron source based on high intensity proton accelerator will be an optimum approach to the production of the radionuclides for cancer therapy.