It is a structured way of observing and describing a patient's current state of mind, under the domains of appearance, attitude, behavior, mood and affect, speech, thought process, thought content, perception, cognition, insight and judgement.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.