The Anatomical Therapeutic Chemical Classification System with Defined Daily Doses (ATC/DDD)


The ATC/DDD system classifies therapeutic drugs. The purpose of the ATC/DDD system is to serve as a tool for drug utilization research in order to improve quality of drug use.

Classification structure

In the ATC classification system, the drugs are divided into different groups according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties. Drugs are classified into five different levels. Drug consumption statistics (international and other levels) can be presented for each of these five levels.

Administrative status

Creation date:

The Guidelines were published for the first time in the current format in 1990.

The Index was published as a paper copy in the current format in 1990 for the first time.

The system has been in use for statistics since 1975.

Last date change: 2003

Annual updates, now in Version 6 for the Guidelines in the current format and Version 13 for the Index in the current format . Available indexes:

Reference documents

ATC Index with DDDs 2003. Guidelines for ATC classification and DDD assignment 2003.

Available formats:

The Guidelines are published in all 3 languages in paper format only.

Online searchable database.

Training and training materials:

2 days international course in Oslo, once a year. The course offers lectures and working groups.

Courses elsewhere on request. Approx. 2 additional courses annually.


The participants receive the Index and the Guidelines, copies of all the presentations, and the working group problems.

The Index is published in the following languages and formats:

English (all available indexes),

German (paper version only),

Relationships with other classifications

Spanish (paper version only)

Correspondence between revisions

The Anatomical Therapeutic Classification (AT) developed by the European Pharmaceutical Market Research Assiciation (EPhMRA). The ATC/DDD system and the AT classification have the same origin, but are developed for different purposes. Comparative tables are available.

Correspondence with international, multinational, national classifications

Relationships with other terminologies

Currently, the ICD contains no reference to any external classification of medical substances. However, guidelines for the ICD-10 section "Poisoning by drugs, medicaments and biological substances" (T36-T50) could contain suggestions on how to combine, or replace, ICD codes with specific substance codes, preferably using an internationally widespread and recommended standard system such as the ATC.


The ATC classification uses the INN (International Non-proprietary Name) whenever possible.

Contact information:

WHO Collaborating Centre for Drug Statistics Methodology

Name a person.

Norwegian Institute of Public Health

P.O.BOX 4404 Nydalen

NO-0304 Oslo