Each year in mid-December, officials from the 56 OSCE participating States gather in Vienna to exchange information on their armed forces, military organization, manpower and major weapon and equipment systems. The countries also share information on their defence planning and budgets during the year. This comprehensive information exchange takes place in accordance with the most important confidence- and security- building measure (CSBM) in the OSCE area - the Vienna Document 1999.

Negotiations on confidence- and security-building measures date back to the first Conference on Security and Co-operation in Europe in Helsinki in 1975. The third follow-up meeting, which took place in Vienna from 1986 to 1989, agreed that two parallel lines of negotiation would be held, one on CSBMs and the other between the 23 states that belonged to NATO or the Warsaw Pact on conventional armed forces in Europe (which led to the CFE Treaty).

The CSBMs negotiations led to the adoption of the Vienna Document in 1990. The politically-binding agreement provides for the exchange and verification of information about armed forces and military activities.

The Vienna Document requires participating States to:

• provide each other with information about their military forces annually, including about manpower and major conventional weapon- and equipment systems, as well as deployment plans and budgets.
• notify each other ahead of time about major military activities such as exercises.
• accept up to three inspections of their military sites per year. Some sensitive areas are excluded.
• invite other States to observe certain activities. It also encourages States to permit journalists from all participating States to cover the activities.
• to consult and co-operate in case of unusual military activity or increasing tensions. The Vienna Document encourages participating States, for example, to voluntarily host military visits to dispel concerns.

The Vienna Document was updated in 1992, 1994 and 1999 to account for the changing needs of OSCE participating States. The latest update introduced a chapter on regional measures that provides a framework for bilateral verification activities.

Participating States in September 2010 agreed to start updating its chapters V, on the notification of military activities, and IX, which concerns the conduct of inspection and evaluation visits.