In this article, discourse analysis, combined with lesbian feminist politics, are used to explore subtle forms of heterosexism in language, a social phenomenon that I have termed "mundane heterosexism," because of its everyday nature. Drawing on feminist understandings of subtle sexism and discursive psychology I analyse three forms of mundane heterosexism derived from (predominantly) tape-recorded antiheterosexism training session data: (1) prejudice against the heterosexual, (2) nonheterosexuality as a deficit and (3) refusing diversity. Two levels for challenging mundane heterosexism are discussed. interactional counterarguments, and broader societal campaigns. I conclude by advocating the necessity of further detailed analyses of the construction of mundane heterosexism, and stress the importance of heterosexism for feminist research. (C) 2001 Elsevier Science Ltd. All rights reserved.