Silence as state conduct plays a significant role in various contexts in the relationships among states and has important practical application in the settlement of disputes by international tribunals. This article examines silence as an element of state behaviour having legal effects in the relationships among states. The question this article seeks to answer concerns the stand international tribunals have taken in the voluntarism/objectivism debate regarding the legal value of state silence. To answer this question, this article analyses the conditions under which silence may acquire legal significance, especially related to the materialisation of the legal concept of acquiescence, according to the jurisprudence of the ICJ and arbitral tribunals. Despite the fact that, as has been suggested elsewhere, the circumstances for the interpretation of silence are a matter of fact and not of law, the ICJ and arbitral tribunals have been consistent in the use of specific conditions on the basis of which silence may be deemed to have legal significance. Conclusions drawn from the utilisation of these criteria may provide some answers to the question whether it is the intention of the silent state or the impact of silence upon other states which gives silence legal value.