Recently, the transparency of customer service and organization administration has been required in many fields. Objective evaluation by a third person is necessary. This also applies to medical institutions; whether the responsibility for explanation to patients and the transparency of medical activities are open is currently emphasized. ISO15189, which specifically applies to clinical laboratories, is an international standard issued in 2003. This standard has commonly been employed as an accreditation tool for clinical laboratories in Europe and Australia. In Japan, the Japan Accreditation Board for Conformity Assessment (JAB) introduced this system as an accreditation tool for clinical laboratories in cooperation with the Japanese Committee for Clinical Laboratory Standards (JCCLS) in 2004. In April 2005, accreditation work was started. Among the ISO systems, ISO15189 is perhaps the first standard specialized in the field of medical practice. This reflects the fact that the importance of clinical examination is internationally recognized. In this report, we summarize the process via which our laboratory was awarded this ISO and the situation in which we passed two surveillances.