Mobile devices are becoming more common in health care and studies show that they can contribute with a lot of benefits. The purpose of this thesis is to investigate what important factors should be considered when designing an application for a tablet computer to be used at an emergency department. The project involved creating a prototype for an application that would be used as a decision support system for doctors when a stroke patient arrives to the emergency department – a case where time and accuracy are both equally important. Research was conducted by doing field studies and interviews, and the results from these helped to develop a prototype. Usability tests were conducted on the prototype and changes were made accordingly. The study showed that there are many important factors to consider; e.g. identifying the workflows, creating a non-linear system and overview support.