In an emergency medical services (EMS) system, a certain number of events come to the attention of the pre-hospital subsystem that are subsequently characterized as having required “life-supportive” care. Such cases represent an undetermined portion of the persons, in the population served, who actually require such care. Generally, the life-support units that are available in a community are dispatched on the basis of information received at a medical emergency dispatching center. Very often, the information obtained from the caller is too ambiguous for a clear decision and, inevitably, there is a significant portion of “false-positive” or inappropriate runs. In systems in which little or no attempt is made to screen calls, the dispatching procedure inevitably becomes a “first come, first served” phenomenon and the inappropriateness of the responses is bound to be even greater.