Clinical thermometers are widely used for measurement of temperature of a human body. Requirements for their performance are written in several standards (ASTM, EN, JIS, etc). Some requirements are similar, while others differ from each other. A few years ago International Organization for Standardization (ISO) and International Organization for Legal Metrology (OIML) agreed that it is necessary to unify the requirements for clinical thermometers from several standards. They formed a joint working group under leadership of the ISO with the task to develop a new standard for clinical thermometers, which would cover all present types of clinical thermometers. The OIML would later adopt the ISO standard as an OIML standard.