Many laboratory managers like to have some proof of their laboratory's participation in our proficiency test scheme, preferably in the form of a certificate that can be copied for auditors or clients. Our institute decided to start offering such 'Certificates of Participation'. The certificates are available since October 1, 2004. Besides the participation in our program, the performance in a specific round can also be the subject of a certificate. Our institute decided to issue a special 'Certificate of Excellence' for a laboratory with outstanding performance, this is when all reported results of the respective laboratory are within the reproducibility limits of the target methods selected. This means that if only one laboratory result is outside the reproducibility limits of the target method, only a 'Certificate of Participation' can be issued. The certificates are only prepared upon receipt of a written order from the laboratory before the start of a proficiency test. A fee of 20 Euros per certificate will be charged for this service.