The first Workshop on 'Nuclear Proficiency Testing' (PT) focused on the new topic appeared at the junction of the nuclear basic research, metrology, quality control in applications, and the new 'Science of Analytical Performance' (SAP), namely: 'how to get/prove the most accurate and precise scientific/technical results in the current practice. Any analytical laboratory should fulfill this goal in order to assure the public credibility of its results, either it is part of the scientific research institute, or a laboratory dedicated to the routine control of the environment, industry, health /medicine, radioprotection, or dosimetry, as the quality of the analytical results and of the services that will be further used depend critically on the accuracy and validity of measurements (EN ISO/IEC Standard 17025: 2005). 'Proficiency Testing' plays a central role in this process as the best tool to prove and certify the Laboratory's Performance & Competence; it belongs to SAP, which, in our case, should be called SNAP (Science of the Nuclear Analytical Performance), as it concerns performance in applications of the nuclear analytical techniques. The 'PT Workshop-2007' created the opportunity to learn the criteria / tools used for interpreting the experimental results and evaluating performance, 'how to fit' the laboratory's performance with the rigor of international 'Proficiency Testing' evaluation, to understand the basic aspects of methods validation and traceability of the nuclear physical quantities to SI, use of the reference materials and of the statistic criteria for the fitness-for-purpose objectives, advantages of the ILC /PT exercises, and how to get the 'Excellence'; so, it was primarily a 'school' , but not only, because the meeting was also a framework for participants to present their latest results and developments. The unique feature of the 'PT Workshop-2007' was the participation -for the first time in a scientific meeting of experts intimately involved in the development of International and National Standards and the organization of international Inter-Laboratory Comparison (ILC) and Proficiency Testing (PT) exercises, of experts involved in radionuclide metrology, who generally establish the norms and requirements for the accuracy of measurements and analytical methods, and experts and specialists involved in nuclear application, as 'lectors'. Their presence and lessons assured the highest level of knowledge for a successful 'school' in the field of Nuclear Proficiency Testing, and the discussions they created were very fruitful, to the benefit of all the participants.