Principles of biological standardization and the conduct of collaborative studies to establish international standards.

: Principles of biological standardisation, based on the use of international standards, are discussed. Procedures are outlined for checking that a material has the properties required of a standard ie uniformity, stability and suitability to serve as a measure for biological activity. Particular consideration is given to the work involved in collaborative studies which are carried out to assess the suitability of a candidate standard to serve as a yardstick for the measurement of the biological activity of test samples likely to be assayed against it.