Trust funds at UNEP are earmarked by donors for specific purposes. The general-purpose trust funds provide financial resources for activities supporting the programme of work of UNEP as well as of conventions and regional seas programmes and the activities of their secretariats.

The biggest trust fund is the one for the Multilateral Fund under the Montreal Protocol on substances that deplete the Ozone layer, for which UNEP’s role is largely that of treasurer.
The Technical Co-operation trust funds are used to facilitate technical assistance to developing countries and also for financing personnel through Junior Professional Officer Programmes and the secondment of staff from donor countries.
Trust funds often have a different governing structure from that of the Environment Fund, may be bilateral or multilateral and are accounted for separately.

The number of trust funds and their expenditures have increased steadily over the years. The overall rise has primarily been due to the three following factors:
1. The growing number of conventions, regional seas programmes administered by UNEP;

2. The increasing amount of technical co-operation activities being financed from trust funds;

3. The growing number of staff seconded to the UNEP secretariat and paid for under trust funds.

By 1992, UNEP managed 43 trust funds. From 1998 UNEP separated the financial reporting on the trust funds directly supporting the UNEP's Programme of Work (48 trust funds) from other trust funds i.e. conventions, which are managed by independent governing bodies (26 trust funds). In 1998-99 the direct support to programme from trust funds amounted to US$32.13 million and in 2004-2005 to approximately US$80 million. Please click here for more

The number of trust funds directly supportin the UNEP programme of work has reduced from 74 in 2003 to 69 in 2006. This number is expected to further decrease by the end of the biennium 2006-2007 due to closure of inactive trustfunds.