At the World Summit in 2005, United Nations Member States unanimously endorsed the‘Responsibility to Protect’. Th is acknowledged the responsibility of states to protect their populationsfrom genocide and mass atrocities, but also that of the international community, acting‘through the United Nations’. A strong focus of the statement is on the necessity of prevention,and the appropriate ‘diplomatic, humanitarian and other peaceful means’ the United Nationscan employ in its service. But what capacity does the United Nations currently have to helpprotect populations from genocide, war crimes, crimes against humanity and ethnic cleansingthrough preventative action? Is it adequate, or are there areas where capacity building is required?Th is paper will explore the current capacity to meet the preventive component of the responsibilityto protect within the United Nations system. It identifi es areas of strength, such as theSecretariat, that might be more explicitly utilised in support of prevention measures. It considersareas in which there are opportunities for improvement, such as through integrating responsibilityto protect considerations into normal operating procedures within relevant UN bodies, andincreasing the focus on longer-term structural prevention. Substantial capacity for mass atrocityprevention currently exists within the UN system, but there are also a number of ways in whichthat capacity can be strengthened.