This Safety Guide, co-sponsored by PAHO and WHO, provides recommendations on how safety requirements may be fulfilled for the protection of patients, comforters and visitors of patients against exposure to ionizing radiation in medical practice in compliance with Appendix II (Medical Exposure) of Safety Series No. 115, International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources (1996). Recommendations cover the establishment of guidance levels for diagnostic medical exposures, acceptance testing processes for radiation equipment, calibration of radiotherapy units and reporting of accidental medical exposures.