Introduction: This paper presents a study of prehospital care with particular focus on how ambulance personnel prepare themselves for their everyday assignments. Methods: The caring science field study took a phenomenological approach, where data were analyzed for meaning. Two specialist ambulance nurses, three registered nurses, and six paramedics participated. Results: The previously known discrepancy between in-hospital care and prehospital care was further interpreted in this study. The pre-information from an emergency medical dispatch (EMD) center provides ambulance personnel with basic expectations as to what they will have to take care of. At the same time that they maintain their certainty and control, our major findings indicate that prehospital care in emergency medical service requires the personnel to be prepared for an open and flexible encounter with the patient; to be prepared for the unprepared, i.e., to be open and to avoid being governed by predetermined statements. Discussion: Our findings suggest that the outcomes of good prehospital care affect patient security. The seemingly time-consuming dialogue with the patient facilitates understanding and decision-making regarding the patient's medical needs, and it is comforting to the patient. The ambulance personnel need to be well prepared for this task and fully understand that the situation might differ considerably from the information provided by the EMD centers. All objective information is of great value in this care context, but ultimately it is the patient who provides reliable information about her/his own situation. © 2012 Emergency Nurses Association.