Sudden cardiac arrest (SCA) is one of the leading causes of death in the western world, affecting about 700 000 people in Europe every year. Multiple causes can underlie SCA, though ischemic heart disease is the most common. SCA is classified as either cardiac or non-cardiac, depending on whether the heart’s pumping function or oxygenation in the lungs primarily initiated a cardiac arrhythmia.In the setting of an out-of-hospital cardiac arrest (OHCA), the purpose of basic life support is to maintain a minimal degree of circulation, in an attempt to maintain a viable, shock responsive heart. Multiple studies, including several included in this paper, have established that early bystander CPR (Cardiopulmonary Resuscitation) enhances survival in (OHCA).The current guidelines issued in 2005 recommend 30 compressions followed by 2 ventilations, the basis of the ratio being partly empirical. Compared to the former guidelines, the 2005 guidelines give more emphasis to compressions, especially in the first minutes of SCA of cardiac origin. Sustaining this trend, new data actually suggest that continuous chest compressions (CCC) may have equal or better effect on survival in SCA of cardiac origin and that it could increase the rate of bystander action and thus increase overall survival. What evidence is there to support the advantages of CCC versus standard CPR (S-CPR)? In which circumstances do these advantages apply? Is the evidence strong enough to endorse an alteration of the 2005 guidelines?In order to answer these questions, three animal studies and ten studies on humans, that compare CCC and S-CPR in the setting of a witnessed out-of-hospital cardiac arrest (OHCA), were evaluated in this paper. One of the animal studies showed significantly increased survival in the CCC group. However, the presence of a secure airway (open endotracheal tube) may have affected the authenticity of the results. On the other hand, the other two studies with obstructed airways (tube closed for passive inspiration), did not identify any significant difference between the group. Seven of the studies on humans were observational, which in itself greatly increases the risk of confounders. Among these, one was conducted on children. All the studies except for one, found no overall significant difference between the CCC and S-CPR groups, in the separate cohorts. The study, that assessed cardiac arrest of non cardiac origin only, registered a better neurological survival for the S-CPR group. The three remaining studies were randomized, and bystanders were instructed to perform either CCC or S-CPR. No significant differences were identified.In other words the results remain inconclusive as to whether CCC or S-CPR has the best outcome in OHCA, except in the non-cardiac group, in which ventilations are of great importance.