This package of materials is designed to enable physicians, psychologists and other busy mental health professionals to quickly develop preliminary diagnoses of patients during an initial brief interview. The IDCL Checklists set contains the WHO Symptom Checklist, which helps the busy clinician to make a preliminary classification. Also contained are the 32 International Diagnostic Checklists (IDCL), which take into account the ICD-10 Research Criteria. These checklists can be used to make a careful evaluation of the symptoms and classification criteria, and thus help to arrive at precise diagnoses according to the ICD-10 classification. Also included is the symptom glossary, which provides succinct definitions of the various symptoms that should be evaluated when using the ICD-10 Symptom Checklist. The checklist system provides a virtual 1-2-3 flow chart which helps the clinician consider many possibilities and quickly focus in on a well-supported classification.