This survey was performed in order to investigate the incidence of adverse reactions to radiopharmaceuticals and defect products in FY2004 in Japan. It was based on responses to questionnaires sent to nuclear medicine institutions. The reply was obtained from 968 institutions among 1,220 to which the questionnaire had been sent. Sixteen cases of adverse reactions were reported. A total of 1,277,906 radiopharmaceutical administrations was reported. The incidence of adverse reactions per 100,000 cases was 1.3. Eight cases of defect products were reported, and the incidence of defect products per 100,000 cases was 0.6.