This paper addresses the question of interaction between home and international students using qualitative data from 100 home students at two "teaching intensive" universities in the southwest of England. Stephan and Stephan's Integrated Threat Theory is used to analyse the data, finding evidence for all four types of threat that they predict when outgroups interact. It is found that home students perceive threats to their academic success and group identity from the presence of international students on the campus and in the classroom. These are linked to anxieties around "mindful" forms of interaction and a taboo around the discussion of difference, leading to a "passive xenophobia" for the majority. The paper concludes that Integrated Threat Theory is a useful tool in critiquing the "internationalisation at home" agenda, making suggestions for policies and practices that may alleviate perceived threats, thereby improving the quality and outcomes of intercultural interaction. (Contains 1 table and 2 notes.)