The leitmotif of this study emphases on the inter-ethnic conflict and eviction between Amhara and Oromo in Oromia National Regional State/ONRS/ special focus on East Wollega. Basically, the study was carried out to scrutinize post-1991 nature, causes and consequences of inter-ethnic conflicts between Amhara and Oromo after the structure of constituent states of our country Ethiopia organized based on ethnic lines/with the introduction of ethic federalism/. The conclusion clearly stipulated the instigation of local officials and authorities were a prominent factor besides the other social, environmental, cultural and economic causes for the activation of ethnic conflict between Amhara and Oromo ethnic groups in East Wollega, Oromia.