The book highlights the importance of measuring and controlling the humidity of industrial materials and agricultural products, regulated by state standards of the USSR. Methods of measuring humidity of various solid, loose, fibrous and other materials, liquid and gaseous products and substances, both provided for by standards and used in modern instrument making, are considered. Data on modern automatic industrial and laboratory devices for express determination of humidity of various materials and considerations on the possibility of their use in assessing the compliance of products with the requirements of standards are presented. The principles of constructing calibration schemes for moisture meters of solids, liquids and gases are briefly considered, the implementation of which will allow the state verification service to control automatic moisture meters used in various sectors of the national economy. The book is designed for a wide contingent of standardization workers, state supervision laboratories for the implementation and observance of standards and the state of measuring equipment (LGN), as well as novice metrologists and verification technicians.