With the present Badgastein Symposium "Radioactive Isotopes in Clinical Medicine and Research" we have now had 40 years of an uninterrupted series of Badgastein meetings on nuclear medicine, since the first one took place in January 1954. We believe that this anni­ versary is worth mentioning. The 21 st symposium proved again to offer a representative cross­ section through the current topics of scientific interest of nuclear medicine. The general theme of research in nuclear medicine has shifted from the spectacular new developments which were so often reported in the first symposia to a less spectacular, albeit equally important period, which may best be characterized by validation and standardization. While this may not be as exciting as we would like it to be, it is nevertheless vital for nuclear medicine to maintain and improve its standing amongst the other specialties of medicine which draw upon the services that nuclear medicine offers.