Drawing upon recent research, this article reviews the theory underlying the use of socioscientific issues (SSI) in science education. We begin with a definition and rationale for SSI and note the importance of SSI for advancing functional scientific literacy. We then examine the various roles of context, teachers, and students in SSI lessons as well as the importance of classroom discourse, including sociomoral discourse, argumentation, discussion, and debate. Finally, we discuss how SSI units, which encourage evidence-based decisionmaking and compromise, can improve critical thinking, contribute to character education, and provide an interesting context for teaching required science content.