The Biological Weapons Convention requires Parties not to develop, produce, stockpile, or acquire biological agents or toxins "of types and in quantities that have no justification for prophylactic, protective, and other peaceful purposes," as well as weapons and means of delivery. The United States unilaterally renounced biological and toxin weapons in 1969.

The Biological Weapons Convention was opened for signature in April 1972 and the United States submitted its instruments of ratification in March 1975. The United States, along with the United Kingdom and the Russian Federation, are the three depositary governments for the Convention. There are currently some 139 States Parties with an additional 18 countries who have signed but not ratified the Convention.

There have been three Review Conferences to the BWC, each taking place in Geneva. The First Review Conference was held in 1980. At the Second Review Conference, in 1986, States Parties agreed on a set of confidence building measures, which included: exchanging data on research laboratories that meet very high national or international safety standards; sharing information on all outbreaks of infectious diseases or similar occurrences caused by toxins which deviate from the normal; encouraging publication of results of biological defense research in scientific journals generally available to the public; and promoting scientific contact, including joint research projects directly related to the Convention.

At the Third Review Conference in 1991, States Parties were determined to strengthen the CBMs and to enhance confidence in the implementation of the Convention. In addition to strengthening the existing CBMs, States Parties added two additional CBMs: declaration of past activities in offensive and/or defensive biological research and development programs; and declaration of vaccine production facilities.

In a further effort to strengthen the effectiveness and improve implementation of the Convention, States Parties mandated the convening of an Ad Hoc Group of Governmental Experts to identify and examine potential verification measures from a scientific and technical standpoint. Also known as VEREX, the Ad Hoc Group held four sessions in Geneva between March 1992 and September 1993, completing its work and submitting a consensus report circulated to all States Parties. As provided in the mandate, a majority of States Parties called for a Special Conference in 1994 to consider the Final Report and determine further actions.

The VEREX Report has four principal sections. Three of the four sections consist of annexes to the Report detailing the specific findings respectively of the first three sessions of the Group. Annex No.1 summarizes the first meeting, held March 30 - April 10, 1992. At this initial session, 21 potential verification measures encompassing both on and off-site activities were identified under the three broad areas of development, acquisition or production, and stockpiling. The off-site measures included the categories of information monitoring, data exchange, remote sensing, and inspections. Exchange visits, inspections, and continuous monitoring comprised the three categories of on-site activities.

Annex No. 2 contains the summary of the examination of each of the 21 potential measures conducted at the second session, held November 23 - December 4, 1992. As part of the examination, the measures were defined and their characteristics enumerated. In addition, the state-of-the-art applicable technologies were detailed, and the capabilities and limitations of those technologies described. Annex No. 3 contains the summary of the evaluation of the measures conducted during the third meeting, held May 24 - June 4, 1993. The 21 measures were evaluated in accordance with the six main criteria mandated by the 1991 Review Conference. For each of the measures, the capabilities and limitations were identified and compiled. In addition, the VEREX assessed illustrative, but not exhaustive, examples of measures in combination.

The fourth component of the Report is a Summary containing an overview of the proceedings and findings of the VEREX which was prepared at the final session, held September 13 - 24, 1993. The principal conclusions of the Summary are:

• The Ad Hoc Group of Governmental Experts (VEREX) concluded that potential verification measures as identified and evaluated could be useful to varying degrees in enhancing confidence, through increased transparency, that States Parties were fulfilling their obligations under the BWC.

• While it was agreed that reliance could not be placed on any single measure to differentiate conclusively between prohibited and permitted activity and to resolve ambiguities about compliance, it was also agreed that the measures could provide information of varying utility in strengthening the BWC.

• Some measures in combination could provide enhanced capabilities by increasing, for example, the focus and improving the quality of information, thereby improving the possibility of differentiating between prohibited and permitted activities and of resolving ambiguities about compliance.

• Concern was expressed that the implementation of any measure should ensure that sensitive commercial proprietary information and national security needs are protected.

• Based on the examination and evaluation of the measures against the criteria given in the mandate, the VEREX considered, from the scientific and technical standpoint, that some of the potential verification measures would contribute to strengthening the effectiveness and improving the implementation of the Convention, also recognizing that appropriate and effective verification could reinforce the Convention.

As provided in the mandate, a Special Conference to discuss the VEREX Final Report and to consider further actions was convened in September 1994. The Conference agreed to establish an Ad Hoc Group, open to all States Parties, to consider appropriate measures, including possible verification measures, and draft proposals to strengthen the Convention in a legally binding instrument.

The Ad Hoc Group held three meetings in 1995, a procedural meeting and two substantive meetings, and two substantive meetings in 1996, each of two weeks duration. The work of the Ad Hoc Group is divided into four Friends of the Chair, consistent with the categories established by the Special Conference. They are Measures to Promote Compliance; Definitions and Objective Criteria; Article X (technology transfer); and Confidence Building Measures (CBMs). An Ad Hoc Group Progress Report will be submitted to the Fourth Review Conference scheduled to convene in Geneva, November 25 - December 6, 1996.