The mental status examination (MSE) is an important part of the clinical assessment process in neurological and psychiatric practice. It is a structured way of observing and describing a patient's psychological functioning at a given point in time, under the domains of appearance, attitude, behavior, mood and affect, speech, thought process, thought content, perception, cognition, insight, and judgment. There are some minor variations in the subdivision of the MSE and the sequence and names of MSE domains. The purpose of the MSE is to obtain a comprehensive cross-sectional description of the patient's mental state, which, when combined with the biographical and historical information of the psychiatric history, allows the clinician to make an accurate diagnosis and formulation, which are required for coherent treatment planning. The data are collected through a combination of direct and indirect means: unstructured observation while obtaining the biographical and social information, focused questions about current symptoms, and formalised psychological tests. The MSE is not to be confused with the Mini–Mental State Examination (MMSE), which is a brief neuropsychological screening test for dementia. Theoretical foundations The MSE derives from an approach to psychiatry known as descriptive psychopathology or descriptive phenomenology, which developed from the work of the philosopher and psychiatrist Karl Jaspers. From Jaspers' perspective it was assumed that the only way to comprehend a patient's experience is through his or her own description (through an approach of empathic and non-theoretical enquiry), as distinct from an interpretive or psychoanalytic approach which assumes the analyst might understand experiences or processes of which the patient is unaware, such as defense mechanisms or unconscious drives. In practice, the MSE is a blend of empathic descriptive phenomenology and empirical clinical observation. It has been argued that the term phenomenology has become corrupted in clinical psychiatry: current usage, as a set of supposedly objective descriptions of a psychiatric patient (a synonym for signs and symptoms), is incompatible with the original meaning which was concerned with comprehending a patient's subjective experience. Application The mental status examination is a core skill of qualified (mental) health personnel. It is a key part of the initial psychiatric assessment in an outpatient or psychiatric hospital setting. It is a systematic collection of data based on observation of the patient's behavior while the patient is in the clinician's view during the interview. The purpose is to obtain evidence of symptoms and signs of mental disorders, including danger to