Advanced ambulance service (Emergency Medical Services/EMS) is considered to be an integral part of emergency medical care as the first assets responding to emergencies and disasters in the prehospital setting in most developed countries.The aim of this study was to evaluate the current situation of Shiraz's EMS by comparing data obtained during two different time periods.This is a retrospective analytic and comparative study in which data obtained from Shiraz EMS during two one-year periods (21st of March 2011 to 20th of March 2012 and 22nd of September 1999 to 21st of September 2000) were compared. Furthermore, these data were also compared with available data from Gothenburg's EMS (2010).Of 84084 missions performed by Shiraz EMS during one year trauma cases were the most common [39282 (46.7%)]. The most common cause of trauma was road traffic accidents (RTA) (27257; 76.5%). Near 56% of all patients were transported to hospitals; some 47% by ambulances and 8.8% by private cars. Around 36.2% of patients received definitive medical treatment at the scene. While there was an increase in response and evacuation times, the number of deaths at scene before ambulance arrival decreased.Although Shiraz's EMS has expanded during last decade and the mortality rate at scene has decreased, the number of RTA-related trauma cases, along with the response and evacuation time, has increased. More than one third of the patients received definitive treatment and could be dismissed directly from the scene. Standardized triage and treatment protocols are needed to improve the EMS activity.