The objective of this study was to systematically review studies on out-of-hospital cardiac arrest published according to the Utstein guidelines to describe the variability in factors of resuscitation and outcome. Articles that reported primary data on survival after out-of-hospital cardiac arrest in the Utstein style were included. Forty-seven articles were identified using Medline. Fourteen studies met our criteria for inclusion. The number of patients in whom resuscitation was attempted varied between 78 and 3,243. The proportion of bystander-witnessed cases varied between 38% and 89%; bystander CPR was performed in 21% to 56% of the cases. Patients with a bystander-witnessed cardiac arrest of cardiac etiology were discharged alive in 2% to 49% of the cases. Even when data are reported in a uniform way as suggested by the Utstein template, there is a tremendous variability in outcome. This did not appear to be entirely explained by variability in the traditional risk factors for a low chance of survival. One cannot exclude the possibility of other factors being of ultimate importance for the outcome.