Generally, the role of doctors has been limited in prevention, diagnosis and treatment of diseases. However, the role has recently expanded in improving the quality of life and evaluating the impairments of various disease. Evaluation of impairment in the psychiatric area has much more difficulty than others. Symptoms of psychiatric disorders have subjective, diverse and changeable. Also, previous tools such as McBride Disability Evaluation, Law of Workmen's Accident Compensation Insurance and Law of National Compensation, are not accepted as universal instruments in psychiatric area because of their own limitation. Consequently, the Department of Impairment Evaluation Committee in Korean Neuropsychiatric Association has revised, evaluated and investigated previous diverse guidelines related with evaluation of psychiatric impairments to make reasonable and adaptable new guidelines which include recent medical opinions. We hope this guideline could be used pertinently in evaluation of psychiatric impairment in every situations.