The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO), was set up by the State Signatories to the Treaty on 19 November 1996 and carries out the preparatory work needed to ensure the Treaty's effective implementation.

A global verification regime has been established to monitor compliance with the Comprehensive Nuclear Test Ban Treaty (CTBT). The verification regime consists of the following elements:

  • International Monitoring System (IMS)
  • International Data Centre
  • Consultation and clarification process
  • Global communication infrastructure
  • On-site inspections
  • Confidence-building measures.

The Preparatory Commission has two subsidiary bodies: Working Group A (WG A) on administrative and budgetary matters and Working Group B (WG B) on verification issues, as well as an Advisory Group on financial, budgetary and associated administrative issues. The Working Groups submit proposals and recommendations for consideration and adoption by the Preparatory Commission at its plenary sessions.


Explore the International Monitoring System (IMS) by clicking on the interactive CTBTO map.