[en] Some fifty years have passed since Japanese Radiation Hazards Prevention Law was legislated in 1957 and enforced in 1958. More than 4,700 establishments handling radioisotopes or radiation generators including accelerators are now registered to be subject to the law. NUSTEC (Nuclear Safety Technology Center, Japan), serving as the designated agency conducting inspections and other activities for the government as specified by the Radiation Hazards Prevention Law, lists up and presents here accidents of radioisotope-handling examples in a tabulated form to help improvement of safety management or education training. Most of the examples are due to worker's mismanagement or improper use of the equipment or devices and they are taken from published information amounting to 148. (S. Ohno)