The work the Multilateral Fund finances activities on the ground in developing countries is carried out by four implementing agencies, which have contractual agreements with the Executive Committee: the United Nations Environment Programme (UNEP), United Nations Development Programme (UNDP), United Nations Industrial Development Organisation (UNIDO) and the World Bank. Each of them is represented at Executive Committee meetings as observers, and also at the Meetings of Parties.

When the Fund was first established, it was envisaged that UNEP would be responsible for research, data gathering and clearing-house functions, UNDP for feasibility and pre-investment studies and other technical assistance, and the World Bank for administering and managing the programme of investment in alternatives (UNIDO was not one of the original implementing agencies). In practice, their roles have evolved slightly differently:

• The World Bank concentrates on large-scale phase-out and investment projects at plant and country levels.
• UNDP organizes demonstration and investment projects, technical assistance and feasibility studies.
• UNIDO prepares and appraises investment project proposals and implements phase-out schedules at plant level.
• UNEP carries out no investment projects, but rather helps to establish the infrastructure within which projects can proceed. This includes institutional strengthening activities (such as establishing national ozone units within each country), facilitating regional networks, and helping to prepare country programmes, especially for low-volume-consuming countries. UNEP also provides clearing-house functions, and produces a range of training materials. Its Compliance Assistance Programme is geared towards achieving total phase-out, and decentralised most of its resources to the regional level, facilitating direct support to developing countries.

UNEP receives the smallest portion of the Fund’s budget, 5%. The remainder of the Fund’s resources are split amongst UNDP, with 30% of the Fund’s budget, UNIDO, with 20%, and the World Bank, with 45%. In practice they play similar roles in implementing ODS phase-out, though each have developed specific areas of strength.