The Drug Information System (DIS) enables to monitor: incidence (the numbers of newly registered problem drug users); prevalence (the numbers of existing problem users visiting treatment/contact centres in a certain time period or as of a certain date); types of used drugs, manner of their application, frequency of use, their availability, purity; health (but also social consequ ences) of drug use (hepatitis, HIV; social and economic consequences); demographic profile of affected persons (age, sex, employment, education, etc.); time trends showing potential changes of the above specified indicators, including changes in the geographic distribution. Hygienic Service was mandated to create and operate the DIS in the Czech Republic. The system has been in operation since 1 January 1995 and it is based on the monitoring of basic health indicators.

        Key words: drug information system, incidence, prevalence of problem drug users, infectious diseases of drug users, Czech Republic