Diagnostic reference levels (DRL) of the activity of radiopharmaceuticals administered in nuclear medicine were introduced in the Czech Republic in 1997 by act no. 18/1997 and decree of the State Institute of Nuclear Safety no. 184/1997 on requirements to ensure nuclear protection. At individual departments its adherence is ensured by the approved quality assurance programme. Two questionnaire surveys implemented in 1998 and 2001 revealed that two thirds of departments do not have serious problems with adherence to DRL in clinical practice. The remaining third drew attention to too low DRL levels for some examinations. The influence of DRL on mean administered activities of radiopharmaceuticals was investigated as a secondary outcome of investigation of the radiation burden of the population from nuclear medicine in the Czech Republic in 1999. In more than half the examinations, as compared with values for 1995, the mean administered activities of radiopharmaceuticals decreased, in the remainder they increased. These changes led to a resultant decrease in the annual collective effective level during the mentioned period by 2.8man Sv in the population of the Czech Republic. The DRL prevented a rising trend of mean administered activities starting in 1987 when in the Czech Republic the first investigation of this type was conducted.

        Key words: nuclear medicine – diagnostic reference level – radiopharmaceutical – administered activity – radiation burden