In practice the psychiatrist working in a clinical neurosciences centre is likely to have to address three main categories of clinical problems on a daily basis: patients with cognitive impairment, patients who present with neurological disease, and patients who present with physical symptoms. This chapter describes specific drug therapies, and concentrates on medical aspects of psychiatry. Careful clinical assessment reveals the diagnosis in the majority of patients. Psychiatrists should be able to perform a competent basic neurological examination as this often provides the crucial clues to a neuropsychiatric diagnosis. The chapter outlines the principles of assessment and management particularly in relation to commonly encountered conditions. However, the same rules of assessment apply whether it is the everyday work of assessing mood in a patient with multiple sclerosis (MS) or the rarely encountered assessment of a teenager with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).