The objective of this study was to evaluate the effect of reorganization of Estonian emergency medical services (EMS) system. The outcomes of out-of-hospital resuscitation in the Tartu urban area were investigated during the 6-year study period. The main aim of reorganization was to provide rapid access to early defibrillation with simultaneous advanced cardiac life support (ACLS) procedures on the scene. The changes were implemented since summer 1994 in Tartu at first. Quick availability of a mobile intensive care unit for high-risk calls; implementation of standards for resuscitation, and routine systematic, realistic, compulsory ACLS training for all ambulance staff were established. There were 368 out-of-hospital resuscitations. Comparison of periods before and after basic reorganization of EMS system showed that the number of resuscitation attempts had evident tendency to increase. The rates of return of spontaneous circulation and survival in patients with cardiac arrest of presumed cardiac origin increased from 32.5% to 58.6% (P < .05) and from 7.5% to 25.7% (P < .05) respectively. Thus, implementation in the EMS system of mobile intensive care, ACLS units, and standard resuscitation training program diminished mortality from sudden cardiac arrest.