This chapter focuses on the approach to comprehensive geriatric assessment and is not intended to be a comprehensive review of medical diagnosis and treatment. For this the reader is encouraged to consult a textbook of internal medicine or geriatrics. The amount of workup and management of systemic medical complaints should be tailored to the psychiatrist’s level of comfort in this role, as well as the skills and comfort of staff to carry out needed monitoring and treatment. A patient’s functional status (i.e., their ability to perform basic, instrumental, and advanced activities of daily living) represents a core component of a person’s identity and self-worth. For the psychiatrist, understanding the patient’s functional and psychosocial status in addition to underlying systemic medical conditions furnishes the context in which psychiatric morbidity takes place and informs the development of the medical and nonmedical components of the treatment plan. An older adult’s functional status too often is the unrecognized collateral damage of chronic systemic medical and psychiatric illness. Not only can it influence the expression and severity of psychiatric morbidity, but it can also be directly affected by the treatment.