As the ion therapy treatment modality develops, knowledge of ion radiotherapy is growing and is being exchanged within the radiotherapy community. This community includes regulatory bodies, radiotherapy professionals, standards organizations, equipment manufacturers and suppliers. The exchange has contributed to the establishment of good practices to ensure the safety of ion therapy treatment facilities worldwide. The best international practices related to the regulatory control of radiotherapy facilities using ion accelerators have been summarized in this publication. It also provides guidance on facility authorization and inspection, as well as technical safety aspects that are typical and significant for ion accelerators. Although addressed mainly to regulatory bodies for radiation safety control, the publication can also be used by equipment vendors and organizations operating or planning to construct such facilities.