The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is one of important international nuclear non-proliferation and disarmament measures. One of its pillars is the verification mechanism that has been built as an international system of nuclear testing detection to enable the control of observance of the obligations anchored in the CTBT. Despite the great relevance to the global non-proliferation and disarmament efforts, the CTBT is still not in force. The main aim of the article is to summarize the importance of the CTBT and its entry into force not only from the international relations perspective but also from the perspective of the technical implementation of the monitoring system.