A review of the scientific, administrative and popular literature on system status management and vehicle location reveals the following: 1. Historical demand patterns can be used to predict future patterns. 2. If the number of calls exceeds the number of ambulances available, calls must wait for an available ambulance, and this increases response time averages. Response times can be reduced by matching the number of ambulances with the number of calls received (matching supply with demand). 3. Response times can be reduced by dispersing ambulances in a service area and also by placing ambulances near the locations of expected clusters of calls. 4. Ambulance demand patterns fluctuate by hour of day and by day of week. 5. All ambulance services have some sort of procedures and policies for preparing for the next response (system status management). Some use algorithms and step-by-step procedures to prepare for the next call; others rely upon dispatchers to invent them on the spot. 6. Ambulance response times can be improved using dynamic deployment and peak-load staffing, but it is also possible to reduce quality with these techniques. Results are influenced by system design, competence of the managers and commitment of the workforce.