Aims: To describe the epidemiology and factors predicting the prognosis regarding resuscitation of patients with out of hospital cardiac arrests (OHCA) and asystole/ pulseless electrical activity (PEA) as the fist rhythm recorded on arrival of EMS.Methods: Analysis of data collected retrospectively on all patients succumbing to OHCA in the city of Oslo from May 1. 1998 to Dec 31. 2001, and with emphasis on patients where the EMS had initiated resuscitative measures. Results: 1380 patients with OHCA with initially observed arrhythmia other than ventricular fibrillation/ -tachycardia were attended by the EMS within the study period. 567 patients were given resuscitative measures. Of these, 458 (70%) and 109 (30%) were judged as having asystole or PEA, respectively.176 (31%) patients were admitted to hospital with restored spontaneous circulation, and 12 (2%) patients were discharged from hospital alive. The patients discharged alive more often suffered from PEA than asystole compared to the patients who where not admitted to hospital (p < 0,01), more of the OHCA were observed by bystanders (p = 0,05) and they had an electro convertible arrhythmia more often while being resuscitated (p = 0.013). Bystander CPR did not have a significant effect on the survival. Patients with OHCA and who was discharged alive from hospital more frequently (58%, p = 0.02) had their OHCA in areas of Oslo with shorter response intervals (mean response interval <= 4 min). The patients with PEA as first observed arrhythmia were onaverage older than the patients with asystole (66 yrs vs. 56 yrs, p < 0,01) and the patients with PEA more often had a collapse observed by bystanders (82% vs. 55%, p < 0,01). 24 % of the patients admitted to hospital and transferred to an ICU, CCU or general ward (n = 112) died within 24 hours and 90 % died in total. Most of these patients were in need of intensive care, 84 % needed respirator support, 42 %received vasopressor treatment, 16 % trombolyttic treatment and 3 % did get PCI the first 24 hours.Conclusion: This study is to our knowledge the second largest study in Scandinavia. It confirms the poor prognosis for OHCA when the first observed arrhythmia is asystole or PEA, but it supplies the EMS personnel with valuable practice. It also confirms many of the factors associated with survival in this patient group, especially a higher survival in the group with PEA.