The authors expected the extent to which host community members (a) perceive immigrants as threatening, (b) believe that the immigrants are able to assimilate to the host community (permeability), and (c) consider their presence in the host community as legitimate to predict attitudes towards immigrant acculturation. The authors designed Study 1 to examine attitudes of Germans toward Turkish immigrants. As expected, ethnocentric acculturation attitudes positively correlated with perceived threat and negatively correlated with perceived legitimacy and perceived permeability. However, only perceived threat contributed uniquely to the prediction of the attitudes. In Study 2, the authors applied an experimental manipulation of perceived threat. Before answering attitude questions, participants read magazine articles with a threatening, enriching, or irrelevant content. The manipulation had the predicted impact on the self-reported attitudes toward immigrants. However, the salience of threatening or enriching aspects of the Turkish culture did not affect implicitly measured attitudes.