The issues of metrological reliability of measuring items are investigated. The conceptual terminology of the theory of reliability is analyzed in relation to measuring items. The regulatory and technical requirements for the reliability of measuring items are considered. The classification of failures of measuring items is carried out. A model is constructed in the form of a tree diagram that characterizes the properties and indicators of the reliability of measuring items. The necessity of standardization of regulatory and technical requirements for the metrological reliability of measuring items is substantiated.