To do anthropology is a political act anywhere in the world, regardless of the anthropologist's degree of awareness and recognition of this fact. Taking the plight of the Yanomami Indians in Brazil and the involvement of Brazilian anthropologists in the defense of indigenous rights, the article discusses the expectations and constrictions involved in anthropological work, particularly in the role of anthropologists as expert witnesses, in the politicized context of interethnic relations. When anthropologists are caught between the demands for "expertise" and their actual capacity to 'represent the Other," their predicament as political actors comes to the fore. However, the author argues, we are agents in a complex political arena, in the field of interethnic relations or anywhere else anthropologists work, whether we like it or not. This article begins the exploration of an important and challenging issue for the next decade of our work.