The cardiovascular and metabolic effects of ketamine as the sole anesthetic agent for surgical correction of fractured neck of femur were studied in eight spontaneously breathing geriatric patients (mean age 83 years) before premedication, at the end of operation, and 15 min and 2 h after the end of anesthesia. Arterial blood pressure, cardiac index, left ventricular stroke work index and oxygen consumption increased during anesthesia but had returned to preoperative levels 15 min after the end of anesthesia. Vascular resistance, heart rate and stroke volume index were not significantly changed. During anesthesia, arterial carbon dioxide tension increased whereas arterial pH and arterial BE decreased. The levels of glucose and lactate increased in both blood and skeletal muscle during anesthesia and remained elevated throughout the period studied but the lactate:pyruvate ratio was unchanged. High energy phosphagen levels in skeletal muscle did not change. Ketamine anesthesia in the spontaneously breathing geriatric patient induces cardiovascular stimulation and metabolic changes indicative of an increased sympathetic stimulation, whereas respiration is slightly depressed. The magnitude of these changes is, however, small and it thus seems that ketamine can be safely used as the sole anesthetic agent for hip fracture surgery in the average geriatric patient.