The primary purpose of this paper is to present a macro-structural theory predicting which groups in a society will be antagonistic towards which other groups, with an eventual aim of understanding why certain societies experience one type of antagonism, while other, apparently similar societies do not. Drawing on many methods of interpreting conflict, the theory argues that intergroup antagonism is caused by a threat that is generated by a change in the level of interaction or stratification within the society. Interaction and stratification also predict the groups involved in antagonistic behavior.