We evaluated the technical and organisational feasibility of a multifunctional telemedicine system in an emergency medical service (EMS) from the user's perspective. The telemedicine system was designed to transmit vital signs data and 12-lead-ECG data, send still pictures and allow voice communication and video transmission from an ambulance. The data were sent to a teleconsultation centre staffed with EMS physicians (tele-EMS physician). The system was used in 157 EMS missions. The applications were used successfully on 80% of missions for real-time vital signs transmission and on 97% for video transmission. The quality of the transmitted still images (n = 64) was: 23% excellent, 50% good, 17% moderate, 9% rather poor and 0% unusable. The quality of the video streaming (n = 36) was: 33% excellent, 56% good, 6% moderate, 6% rather poor and 0% unusable. The tele-EMS physician was able to assist the EMS team in several cases and provided the preliminary information for the hospital in nearly all missions. Use of the telemedical system in EMS is feasible and the quality of the transmitted images and video was satisfactory. However, technical reliability and availability need to be improved prior to routine use.