INTRODUCTION In the Netherlands, a physician-staffed helicopter emergency medical system (HEMS), called the Helicopter Mobile Medical Team (HMMT), provides prehospital care for severely injured patients in addition to ambulance services. This HMMT has proven to increase chances of survival and reduce morbidity. HMMT dispatch is performed following certain dispatch criteria. The goal of this study was to analyze actual dispatch rates and assess the protocol adherence of the emergency dispatchers in Rotterdam regarding HMMT dispatch. METHODS All high priority ambulance runs between April 1 and July 1, 2003, were prospectively documented and cross-referenced to dispatch criteria. It was determined whether the emergency call warranted either immediate dispatch of the HMMT or a secondary dispatch after arrival of the first ambulance. When dispatch actually occurred, this was also documented. RESULTS In The Studied Period A Total Of 5765 A1 Ambulance Runs During Daylight Were Documented. Of These, 1148 Runs Met Primary Dispatch Criteria And 38 Runs Met Secondary Dispatch Criteria. Actual Hmmt Dispatch Occured In 162/1186 (14%) Cases. CONCLUSIONS HEMS dispatch rates and dispatch criteria adherence are low (14%). Better protocol adherence by emergency dispatchers could lead to a sevenfold increase of HMMT dispatches. The reasons for suboptimal protocol adherence remain unclear and persist, despite proven value of the HMMT in reducing patient mortality and morbidity.