Participants: The five participants were appointed by the Council of The Endocrine Society and charged with attaining the objective using published data and expert opinion.

Evidence: Data were gleaned from published sources via online databases (principally PubMed, Ovid MEDLINE, Google Scholar), the College of American Pathologists, and the clinical and laboratory experiences of the participants.

Consensus Process: The statement was an effort of the committee and was reviewed in detail by each member. The Council of The Endocrine Society reviewed a late draft and made specific recommendations.

Conclusions: Laboratory proficiency testing should be based on the ability to measure accurately and precisely samples containing known concentrations of testosterone, not only on agreement with others using the same method. When such standardization is in place, normative values for total and free testosterone should be established for both genders and children, taking into account the many variables that influence serum testosterone concentration.