After the first symposium of this ISRS at Brookhaven National Laboratory, USA in 1976, nearly forty years have passed. ISRS meeting were held as biennial meetings alternately in America, Europe, America, Europe, Asia/Australia. Following the 19th Symposium held at the VU University Medical Center in Amsterdam, the Netherlands, in August 2011, the 20th Symposium will be held in Juju, Korea. On behalf of the Organizing Committee, we’re pleased to announce that the 20th International Symposium on Radiopharmaceutical Sciences will be held at the Jeju International Convention Center (Jeju ICC) in Jeju Island, Korea, May 12-17, 2013.