Proficiency Testing (PT) is defined as evaluation of participant performance against pre-established criteria by means of interlaboratory comparisons. PT provides the quality assurance of laboratory test results as an external quality control tool also, encourages the objective evaluation of analysis and the technical development of the studies, and allows feedbacks. Since 2010 NFRL has been organizing PTs which is one of the main services. PT is accredited to ISO/IEC.  "TS EN ISO / IEC 17043 Conformity Assessment - General Requirements for Proficiency Testing" is an international standard that sets out all the technical and administrative aspects of organizing PTs.  NFRL is the first and only PT provider accredited to this standard in food and feed area and all PTs organized are carried out in accordance with this standard. International standards (ISO 13528, IUPAC protocol) and statistical methods (Huber H15, Q/Hampel etc.) are used in evaluating the results of PTs.