The UN's list of ambassadors & representatives has become full of stars, like Angelina Jolie.
But some stars like Oscar nominee Naomi Watts, could no longer stand by and watch people die. She has been appointed as special representative with the UNAIDS to help fight AIDS.
Watts has just returned from a five day visit to Zambia, where only one in five people stricken with the disease receive treatment.
Other Hollywood stars on the UN list are: Michael Douglas, who promotes arms control as a peace messenger for UN Secretary-General Kofi Annan.
Australian Nicole Kidman also became a goodwill ambassador for the United Nations Development Fund for Women in January.