The anesthetic and perioperative care of geriatric animals requires increased vigilance and support. The margin of acceptable physiological variation is probably more narrow than in younger patients. Underlying disease, which is often subclinical, influences metabolism and recovery from anesthetics and also predisposes the patients to adverse outcome. Limited respiratory and cardiovascular reserve diminishes the ability of many older patients to meet the challenges of anesthesia and surgery or other stressful medical procedures. The psychological, as well as physiological, stress of hospitalization is increased in many geriatric patients.