DSM is the manual used in the medical practice. Psychiatrists use it in order to assess the patients' condition. The manual provides standardized descriptions of mental disorders. The function of DSM is to objectify definitions of disorders and to help physicians in their routine work. The purpose of my presentation is to show how the DSM is a tool for stabilizing a certain way of thinking about mental illness. Basing on the history of creation of manual, I will show how the construction of DSM is similar to creating a laboratory environment in order to solve practical problems in everyday medical diagnostics. Introduction of DSM in the world of medicine resembles implementation of technological innovation. The DSM can be seen as a heterogeneous actor-network which is delegated in the social sphere. I will try to show that this delegation is related to (1) standardization of theory and practice of medical discourse; (2) the creation of specific medical rationality (called by Andrew Lakoff the pharmaceutical reason); (3) biomedicalization process (which is associated with expanding the medical discourse and with commercialization of medical services). I will argue that medical diagnostics is a result of a number of interconnected heterogeneous factors and practices of stabilizing them. I will use the STS concept of laboratory and John Law's theory of long distance control.