Homeostatic reflexes are believed to supply the means by which the body adapts to changes in the environment (posture, temperature, etc.) and, hence, it might be expected that their importance would increase when the body is disturbed by trauma. In fact, these reflexes are largely abandoned in the response to danger (the defense-arousal reaction), and it is only after simple fluid loss that a limited improvement is seen, that is, an increase in the sensitivity of the baroreflex. Whenever tissue damage generates nociceptive C fiber afferent impulses, there is serious and relatively long-lasting inhibition of the baroreflex and of all aspects of neural thermoregulation. Significant changes occur after quite moderate injuries and do not depend on any reduction in tissue oxygenation. In children with burns in whom early pyrexia is common, central thermoregulation may also be affected by cytokine pyrogens. These changes have implications for the management of patients with all types of injuries. However, further analysis is needed if we are to understand these responses and their role in the body's defense; without this knowledge, we shall not be able to modulate them effectively.