This chapter focuses on a particular form or type of ignorance—namely, selective ignorance. It occurs when people produce or disseminate specific sorts of information about a topic or entity while failing to produce or emphasize other information about it. The chapter clarifies the concept of selective ignorance and its relationship to other literature on the topic of ignorance. It shows that this concept can be helpful both from a practical perspective (i.e., recognizing how interest groups can marshal knowledge to advance their goals) and from a theoretical perspective (namely, understanding how information is produced and distributed). The chapter illustrates the significance of selective ignorance in case studies involving agriculture and pollution. The case studies illustrate that the aggressive dissemination of some sorts of information (agricultural techniques), along with efforts to suppress other sorts of information (hazards of polluting chemicals), can generate socially significant forms of selective ignorance.