The protocols for sentinel lymph node biopsy and radioguided occult lesion localization could potentially be of great value in the management of breast cancer patients. Both involve the injection of a 99Tcm-labelled radiopharmaceutical close to or into the lesion, localization of the sentinel lymph node or occult lesion by scintigraphy, and surgical removal with the aid of a hand-held gamma-ray detector. We present dosimetric data on patients and hospital personnel involved in these procedures. For evaluation of radiation protection, we measured the absorbed dose and air kerma rate. Activity levels in excised tissues and surgical instruments were also determined. For patients, the mean absorbed dose to the abdomen was 0.45 mGy, which is low compared to doses received from other diagnostic examinations. For surgeons after 100 operations, the mean absorbed dose to the hands was 0.45 mGy and the mean effective dose 0.09 mSv. Absorbed doses to all hospital personnel involved in the procedures were very low compared to recommended annual limits stipulated by the International Commission on Radiological Protection. We conclude that these procedures, performed according to protocols laid down by the European Institute of Oncology, Milan, are safe from the point of view of radiological protection and that only routine precautions are necessary.