The purpose of this study is to analyse the normative character of custom in international humanitarian law (IHL), on the basis of the theory and jurisprudence of public international law, in order to arrive at a better understanding of the conduct of States in conflict situations. In so doing, an attempt will be made to determine the possibilities for developing custom in IHL, especially in view of the increasing concern shown by international public opinion for the plight of victims of armed conflicts. The paper will begin with a review of the questions raised by custom as an independent source of humanitarian law (point 1) and go on to take a closer look at the constituent elements of custom in humanitarian law (point 2). It will end with a comparative study of the two approaches to custom in IHL, concentrating on the consequences that the development of custom may have in the future (point 3).