In the changing global environment ofdevelopment cooperation, trust funds have emerged as asignificant pillar of the global aid architecture, used toaddress limitations in bilateral aid and fill perceived gapsin the operations of existing multilateral institutions.They currently account for about 11 percent of officialdevelopment assistance (ODA), and they finance a substantialpart of the World Bank's business. The activities theyfund are highly varied, ranging from huge global programswith their own governance structures to conventionaldevelopment projects, debt and disaster relief operations,and technical assistance. This IEG evaluation, undertaken atthe request of World Bank executive directors, assesses thevalue of the trust fund vehicle as a way of delivering aidand the effectiveness and efficiency of the deployment oftrust fund resources. In addition, the evaluation assessesthe Bank's management and accountability for the use oftrust fund resources and the impact of trust funds on theBank's development role. The evaluation finds thatdonors, recipients, and the World Bank have considerableoverlapping interests in this vehicle, but their interestsmay diverge on specific issues such as how trust fundallocation decisions are made and how trust funds aregoverned and managed. Furthermore, while trust funds can addvalue by providing coordinated grant financing for specificcountries, development issues, and especially global publicgoods, the deployment of trust fund resources does notconsistently work in accordance with the Paris Declarationaid principles of country ownership and donor coordination.Notably, many trust funds of global scope involveinsufficient recipient participation and lack clear outcomeobjectives. For other trust funds, a three-pillar approachconsisting of country-specific trust funds; global andregional partnership programs; and multi-donor,multi-recipient umbrella facilities will allow the Bank tostrengthen the effectiveness, efficiency, and accountabilityfor results.