The Geriatric Mental State Examination (GMS) is now established as one of the most commonly used mental health assessments for older people. Its strengths lie in extensive validity studies, high inter-rater reliability, accessibility to trained raters, irrespective of professional background and its continual evolution and adaptation. Its computerisation, association with supplementary instruments and support by a diagnostic algorithm provides a comprehensive diagnostic system and syndrome profile for each subject. The instrument has been validated against most major diagnostic systems and has been used as outcome measures in intervention studies. It has been translated into numerous languages and validated as a diagnostic instrument in various cultures. Such studies have exposed weaknesses, including the over diagnoses of organic states in populations with poorly developed education. On-going studies continue to address these issues, providing a culture sensitive instrument enabling unique trans-cultural research in a relatively under-researched field. Copyright © 2002 John Wiley & Sons, Ltd.