The support systems for the Emergency Medical Services (EMS) at mass gatherings, such as the local marathon or large international baseball games, are underdeveloped. The purposes of this study were to extend well-developed, triage-based, EMS Personal Digital Assistant (PDA) support systems to cover pre-hospital emergency medical services and onsite evaluation forms for the mass gatherings, and to evaluate users ' perceived ease of use and usefulness of the systems in terms of Davis ' Technology Acceptance Model (TAM). The systems were developed based on an established intelligent triage PDA support system and two other forms the general EMS form from the Taipei EMT and the customer-made Mass Gathering Medical form used by a medical center. Twenty-three nurses and six physicians in the medical center, who had served at mass gatherings, were invited to examine the new systems and answer the TAM questionnaire. The PDA systems were composed of 450 information items within 42 screens in 6 categories. The results supported the potential for using triage-based PDA systems at mass gatherings. Overall, most of the subjects agreed that the systems were easy to use and useful for mass gatherings, and they were willing to accept the systems.