Initially seven categories of major conventional weapons, namely: battle tanks, armoured combat vehicles, large calibre artillery systems, combat aircraft, attack helicopters, warships, missiles and missile-launchers, - were covered by the Register.

A regular review of the Register by Groups of Governmental Experts (GGE), including expansion of its scope by the addition of new categories of arms, is an integral part of its operation. In their work, GGE had to consider a number of "politico-military" factors relevant to the establishment of a reporting mechanism consistent with confidence building and issues of regional and international stability, including new security challenges.

The majority of conflicts during the last two decades have not involved considerable amount of major conventional arms. The weapons used were smaller and lighter and specifically not covered by the Register, but fell in with the categories of SALW.

In 2003, when SALW emerged as a major item in the global arms control agenda, an agreement on the Register expansion at the expense of SALW was reached. After intensive debate, the Group agreed upon lowering the reporting threshold for artillery from 100 mm to 75 mm, and the inclusion of MANPADS in Category VII of the Register "Missiles and missile-launchers".

In addition to this, the Group made a recommendation aimed at more transparency in transfer of SALW. Member States, which are in a position to do so, were encouraged to provide additional information on international transfers of SALW. In order to promote preparation and submission of the relevant information to the Register, in 2006 the GGE adopted standardized forms for reporting export and import of SALW.

The reporting of SALW transfers for the last three years has increased both in terms of the number of reporting States, the details of their transfers and the diversity of countries submitting reports (see table).

The progress achieved over this period has imparted an additional dimension to the Register’s value as a source of data on arms transfers. The respective information was included in almost 60 per cent of reports submitted to the Register in 2009. At the same time, neither of five major regional groups reached 100 per cent reporting on SALW transfers so far, though the majority of UN Member States have underlined the importance of increased transparency in this area. Although the submissions of 2010 reports for the UN Register is still in progress, as of 10 June 2010 UNODA has already received 34 reports from Member States, 16 of which contain information on international transfers of small arms and light weapons.