This chapter provides an overview of current trends in the mainstream donor system in development cooperation that comprises members of the Organisation for Economic Co-operation and Development’s (OECD) Development Assistance Committee (DAC). Emerging economies who provide South-South Cooperation are increasingly challenging the existing system and OECD DAC donors are under pressure to justify the relevance of Official Development Assistance (ODA). At the same time, partner countries are questioning donor approaches to aid priorities, channels, and modalities by asking that donors more effectively address partner country needs. The chapter profiles how, as a result, some donor-funded programmes now use frameworks such as results-based management, thinking and working politically, and doing development differently. Still, these ideas compete with an increased emphasis on national interests in both donor and partner countries. OECD DAC donors therefore face the interconnected challenges of building better technical tools for measuring the effects of ODA, improving political communication, and introducing aid modalities that meet partner country needs.