Scholars working in science and technology studies have recently argued that we could learn much about the nature of scientific knowledge by paying closer attention to scientific ignorance. Building on the work of Robert Proctor, this article shows how ignorance can stem from a wide range of selective research choices that incline researchers toward partial, limited understandings of complex phenomena. A recent report produced by the International Assessment of Agricultural Knowledge, Science, and Technology for Development serves as the article's central case study. After arguing that the forms of selective ignorance illustrated in cases like this one are both socially important and difficult to address, I suggest several strategies for responding to them in a socially responsible manner. © The Author(s) 2012.