Elderly patients with unintentional weight loss are at higher risk for infection, depression and death. The leading causes of involuntary weight loss are depression (especially in residents of long-term care facilities), cancer (lung and gastrointestinal malignancies), cardiac disorders and benign gastrointestinal diseases. Medications that may cause nausea and vomiting, dysphagia, dysgeusia and anorexia have been implicated. Polypharmacy can cause unintended weight loss, as can psychotropic medication reduction (i.e., by unmasking problems such as anxiety). A specific cause is not identified in approximately one quarter of elderly patients with unintentional weight loss. A reasonable work-up includes tests dictated by the history and physical examination, a fecal occult blood test, a complete blood count, a chemistry panel, an ultrasensitive thyroid-stimulating hormone test and a urinalysis. Upper gastrointestinal studies have a reasonably high yield in selected patients. Management is directed at treating underlying causes and providing nutritional support. Consideration should be given to the patient's environment and interest in and ability to eat food, the amelioration of symptoms and the provision of adequate nutrition. The U.S. Food and Drug Administration has labeled no appetite stimulants for the treatment of weight loss in the elderly.