In a multi-centre European trial we have assessed the radiation dose to those accompanying patients undergoing nuclear medicine investigations. Dosemeters were first calibrated against each other and then used to measure the radiation dose to the nurse or relative while they were in the waiting room. In departments where there was one waiting room the median radiation dose was 13 microSv, and the corresponding figures for where there were two waiting rooms and where the patients were allowed to leave the department with their nurse or relative were 12 and 11 microSv, respectively. These figures are not significantly different. However, we found that the median radiation dose to relatives was 13 microSv while that to nurses was 3 microSv (P < 0.01), although the waiting times were not significantly different. The reasons for these differences are discussed. Our data do not support the need for a second waiting room for injected patients in a nuclear medicine department.