Cyclotrons are one of the most important sources of radionuclides used in biomedical applications. The production of important radionuclides used in single photon emission tomography techniques such as 123 I, 67 Ga, 201 Tl and 111 In has been based for decades on cyclotrons, typically proton machines with an energy up to 30 MeV. The extraordinary growth of positron emission tomography has led to the development of new models, and to the installation of numerous cyclotrons, typically accelerating protons in the energy range 10 -20 MeV. These have been used for the production of the main PET radionuclides, namely 11 C, 13 N, 15 O and, above all, 18 F. Recently, their use has been extended to the production of radiometals, like 68 Ga, and even to the direct production of 99m Tc.Moreover, cyclotrons are valuable tool for research and education of new scientists. This review presents the main manufacturers and briefly discuss the characteristics of the models they currently offer on the market.