The purpose of this study is to present the notion of mercenaries laid down in literature and in international law, as its applicability to private military companies and their employees so. The first chapter examines the use of the notion of mercenaries in literature and in international treaties. It explores whether the definition laid down in international treaties, reflect customary international law, or not. The second chapter of the study scrutinizes the various conditions listed in the afore-mentioned notions and tries to find out whether and to what degrees private military companies and their employees meet them. The final conclusion of this paper - of the perspective of international law - is that private military companies and their employees, in accordance with the rules of international law, cannot be considered mercenaries. © 2013 Akadémiai Kiadó.