The design of easy-to-use mobile systems for collecting and handling emergency medical care data in the field can significantly improve the effectiveness of rescue operations. In particular, this paper focuses on the design and evaluation of a mobile application that replaces ambulance run paper sheets. First, we discuss the limitations of traditional ambulance run paper sheets. Then, we present the PDA-based system we have developed. Finally, we discuss in detail the usability study we have carried out with first responders.