The paper describes a new methodology that can be useful to researchers and clinicians around the world. The instrument is being used in national surveys in thirty countries and is translated into many languages. Special software programs that generate diagnoses and that facilitate data entry are also available along with a computerized data collection system, adding to the usefulness of the instrument.

Mental disorders are among the most commonly occurring and seriously disabling of all health problems. Yet much less community epidemiological research has been carried out on mental disorders than most physical disorders because of difficulties associated with accurately assessing mental disorders. The WHO Composite International Diagnostic Interview (CIDI) was designed to address this problem by making available a reliable and valid interview schedule and training materials that can be used by researchers to assess the prevalence and correlates of mental disorders.

One of us (Kessler) is the Chair of the WHO CIDI Advisory Committee, the group that is responsible for developing and maintaining the CIDI. The other of us (Ustun) is the Head of the Classification, Assessments and Terminology Group at WHO, the group within WHO responsible for the CIDI.

The CIDI is designed to be used in general population surveys aimed at estimating the prevalence and correlates of mental disorders. The WHO WMH surveys are being carried out to provide basic descriptive information to government health policy planners throughout the world that will call their attention to the high prevalence, high societal costs, and high unmet need for treatment of this devastating class of disorders. Our hope in carrying out the WMH surveys is that these results will have positive effects on the political process that shapes the health policy agenda of governments.