Radionuclides used in nuclear medicine studies are produced in cyclotrons and nuclear reactors. The design and operational principles of these units are described. The mechanism of reactions in the production of radionuclides are elucidated. Target preparation and calculation of the yield of the product are described. Common radionuclides in nuclear medicine along with their production method and other properties are presented in a list. Radionuclide generators as an in-house source of radionuclide is highlighted.