This chapter looks at whether violence within and between groups played an important role in the Palaeolithic and Mesolithic periods. The evidence is based on osteological information, which is limited by preservation and the incomplete osteological record. With regards identified traumatic lesions, it seems problematic to distinguish between accidents and interpersonal violence. The first clear evidence of interpersonal and lethal violence on a large scale is from the Upper and Late Palaeolithic. Current data shows that cases of violent behaviour are evident through the Palaeolithic and Mesolithic periods, some of which gives evidence of group conflict. However, violent behaviour does not occur more often in later or earlier times of the Palaeolithic. Besides the evidence for violent interactions there is also sporadic evidence for treatment and care of trauma and other injuries throughout the Palaeolithic and Mesolithic. The increase in cases of interpersonal violence from the Mesolithic period is most likely related to better preservation and the much higher number of burials and more complete skeletons. Violence is present not only in recent hunter-gatherers and nomadic groups, but also among Palaeolithic and Mesolithic hunter-gatherers.