Interrogative understanding is the epistemic state ascribed by claims of the form ‘S understands why p’. Typically, such attributions are taken to posit a special epistemic relation of understanding-why between a subject S and a proposition p. In the first part of this talk, I argue that attempts to analyse interrogative understanding in terms of this binary relation fail. I then build on these arguments to advance contrastivism about interrogative understanding—i.e., the idea that ‘S understands why p’ posits a three-place relation between a subject S, a proposition p, and a contrast to p, q. As we will see, this proposal avoids the tricky results that afflict the binary views, whilst also providing a neat account of the gradability of interrogative understanding.