As teachers committed to educating all students, we need to learn more about how instructional materials shape representations of sexuality and gender. Through its insistent deconstruction of the norms that structure practice and belief, queer theory offers perspectives from which science educators can question assumptions embedded in textbooks. This article applies queer theory to analyze eight biology textbooks used in the United States. Specifically, we ask how biology textbooks address sexuality outside the heterosexual norm and if they propagate heteronormative attitudes. The textbooks examined offer deafening silences, antiseptic factoids, socially sanitized concepts, and politically correct binary-gendered illustrations. In these textbooks, the term "homosexuality" was used only in the context of AIDS where, along with iv drug users, they were identified as an affected group. The pervasive acceptance of heteronormative behavior privileges students that fit the heterosexual norm, and oppresses through omission and silence those who do not. We offer implications for practice to help science educators broaden their perspectives on the constructs of sexuality and gender to construct new ways of knowing and understanding differences in science classrooms and the natural world.