Triangular co-operation is a relatively recent mode of development co-operation. It normally involves a traditional donor from the ranks of the OECD's Development Assistance Committee (DAC), an emerging donor in the South, and a beneficiary country in the South. It has received increasing international attention because of particular advantages it is said to provide. At the same time, it poses several risks that could further complicate international development co-operation. To make full use of its potential, it is important to conceive it as a learning process, to identify the interests of the three parties involved, and to apply the internationally agreed principles of aid effectiveness. When these principles are applied, triangular co-operation can enrich international development cooperation.