Since 1985, a series of performance tests has been carried out by NRPB on dosimetry services in Great Britain, in partial fulfilment of an approval system operated by the Health and Safety Executive. The main effort has gone into providing performance tests on dosimetry services for external radiations and the results for the years 1985-90 are presented here. Results of tests on dosimetry services for internal radiation are, however, also included. In Great Britain, film badges and thermoluminescence devices are used as personal dosemeters and there dosemeters were irradiated with nominal dose equivalents in the range 0.5-250 mSv. The results have been analysed in terms of bias (systematic error) and random error in each batch of irradiated dosemeters.