Patient falls are a serious problem in hospitals, resulting in substantial morbidity, mortality, length of stay, and costs. The results of a small trial of a patient vigilance system in a post-neurosurgery unit of a large acute care hospital are reported. The system includes two components: (a) passive sensor array placed under the patient in a hospital bed, and (b) a bedside unit that connects to the nurse call system already in place at the hospital. This trial demonstrated the overall effectiveness of the vigilance system in reducing the rate of patient falls. The cost-effectiveness analysis found that use of this system was associated with somewhat higher measured costs. It is likely that the system was cost-saving, due to unmeasured costs.