This document specifies general requirements for proficiency tests that are offered to in vivo bioassay measurement facilities operating a whole-body counter (WBC) or partial body counter (PBC) for monitoring of persons. It specifies minimum requirements for proficiency testing applicable to dosimetry laboratories that have dedicated facilities for in vivo monitoring and where accreditation is required as part of providing the service. It also provides general requirements for proficiency testing that may include a larger group of non-accredited laboratories that may perform measurements as part of worker surveillance or in response to an emergency. This document covers proficiency tests that involve only the quantification of radionuclides and tests that require the identification of radionuclides and their activity. This document does not define specific requirements on administrative aspects of proficiency testing, such as shipping and finance, that may be the subject of national or international regulation.