The laboratory for the preparation of doses of radiopharmaceuticals - the "hot" laboratory is part of the department/clinic for nuclear medicine where radiopharmaceuticals are stored and individual doses are prepared for patients, and is the place with the highest risk of exposure to ionizing radiation. Therefore, access to this area is limited only to personnel who must be trained to handle radioactive sources, and work in this place must be organized in such a way as to reduce the risk of radiation exposure for employees and patients. This paper describes the accommodation, appearance and equipment as well as the organization of work in the hot laboratory. Procedures performed from device control procedures to preparation of individual doses of radiopharmaceuticals for patients are also described, along with records of possible sources of radiation and risks of radiation and contamination in the laboratory. Depending on the possible sources of radiation, radiation protection measures as well as ways to control contamination and radiation exposure are listed. For correct work in the "hot" laboratory, it is necessary to build and equip the room correctly, establish precise and clear procedures for each procedure both during regular work and procedures during extraordinary events, which must be available in written form. In a ˝hot˝ laboratory, there is a risk of exposure to ionizing radiation as well as a risk of contamination from various sources, and the methods and measures of radiation protection differ depending on this. In all this, the radiological technologist working in the "hot" laboratory has a leading role in ensuring the correct operation of this laboratory.