The effects of protein-calorie malnutrition have been assessed in general surgery patients, orthopedic surgery patients, and in liver transplant patients. Protein-calorie malnutrition may be a risk factor for falls and results in increased cholecystokinin responsiveness in geriatric patients. Discussed in this article are: dysphagia, which may result from protein-calorie malnutrition; trace element abnormalities in liver disease; magnesium deficiency, which impairs potassium homeostasis; and pyridoxine deficiency, which alters maternal-infant interactions and may affect human immune function. Scurvy and diarrhea in the American Civil War are reviewed. Also discussed are animal experiments in malnutrition, which attenuates the acute phase response to injury. Macrophage alterations as a consequence of malnutrition are assessed, as are malnutrition, which impairs insulin binding; vitamin E deficiency, which affects serum zinc and copper levels; and maternal folate deficiency, which affects pregnancy outcome.