This article supports critical, social justice oriented science education research by providing a theoretical and methodological basis for examining how subjectivities may be constituted through discourses found in science education texts. Such research explores how discourses orient teachers and students to the world, others, and themselves, as well as outlines "who" can legitimately participate in practices of science education. Subjectivity can be thought of here in its most basic sense--the particular perspectives, beliefs, desires, and convictions held by individual subjects. This article begins by setting a theoretical context for a Foucauldian approach to subjectivity, discourse, and critical discourse analysis (CDA). Next, it provides a methodological background for examining science education curriculum materials. It concludes with a brief discussion of a recent textbook study that examines how biology textbooks can work to constitute subjectivities related to ethics, sex=gender, neocolonialisms, and neoliberalism.