This report examines the successes and challenges of peacemaking efforts of the African Union (AU) and the Organisation of African Unity (OAU) in Burundi between October 1993 and April 2009, and in Comoros between 1995 and March 2009. It asks how and why the OAU/AU became involved in the two countries, and draws lessons from both engagements. The report analyses the political, diplomatic and administrative aspects of the OAU/AU involvement in Burundi and Comoros, and examines the military dimension of the processes. At the heart of the report lies the basic, yet profoundly significant question of how international organisations such as the OAU/AU – challenged by limited resources and capacity – manage peacemaking processes involving high stakes, in intractable intra-state conflicts. The report examines the dilemma of which tools to use to resolve a particular conflict, how to facilitate dialogue among belligerents, how to conduct effective mediation, what support structure to draw on, and how the competing demands and problems that inevitably emerge are addressed. Some lessons are drawn from the diverse tools that the OAU/AU applied in Burundi and Comoros, including shuttle diplomacy, facilitation and mediation; coercive diplomacy; economic sanctions; observer missions and military intervention. Based on the two case studies, the report provides practical recommendations for enhancing AU’s mediation and peacemaking capacity.