Interventions based on neurophysiologic monitoring appear to decrease the incidence of postoperative neurologic sequelae and reduce the length of stay. Inasmuch as the break-even cost for neurophysiologic monitoring is more than four times the actual average charge, both patients and hospital may profit from this service. Because this study was not a truly randomized clinical trial, unintentional statistical bias may have occurred and caution is urged in interpreting the magnitude of apparent intergroup outcome differences.