The document summarizes information about the 4th High Level Forum on Aid Effectiveness (HLF4) taking place in Busan, Korea from November 29th to December 1st, 2011. Over 2000 delegates from donor and developing countries, civil society, and the private sector will attend to assess global progress in improving aid effectiveness, share experiences in delivering results, and agree on commitments in the Busan Outcome Document. Key topics at HLF4 will include building blocks, lessons from prior HLFs in Rome, Paris, and Accra, the roles of developing country systems and civil society, and using evidence to monitor implementation and evaluate progress toward more effective development aid.