© 2016 Elsevier Inc. Assessing the mental status of patients with a neurobehavioral disorder is a critical element in the diagnosis and treatment of these patients. This assessment should always be performed after the patient's history it taken and a general physical as well as a neurologic examination is completed. The mental status examination commences with observing the patient's appearance and level of consciousness. The examiner should also pay attention to patient's social behavior, emotional state and mood. There are 3 major means of assessing a patient's mental status. One type attempts to determine if the patient is demented and the severity of the dementia as it pertains to their ability to perform activities of daily living as well as instrumental activities. A second type of assessment utilizes what may be termed as "screening tests" or "omnibus tests". These brief tests are performed independent of the patient's history and examination. The two most frequently used screening tests are the Mini-Mental Status Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The third means of assessing a patient's mental status is by using specific neuropsychological tests that focus on specific domains of cognition, such as frontal executive functions, attention, episodic verbal and visuospatial memory, declarative knowledge such as language (speech, reading and writing) and arithmetical, as well as visuospatial and perceptual abilities. These neurobehavioral, neuropsychiatric and neuropsychological assessments of patients with a cognitive decline and behavioral abnormalities should often be accompanied by laboratory tests, and neuroimaging that can help determine the underlying pathologic process so that effective therapeutic and management approaches can be provided.