Intonation, the use of voice pitch to communicate meaning at the phrasal level, includes at least three elements in English: prominence, tune, and range. It is an elusive pronunciation feature for many teachers, who are uncertain about what it includes, what kinds of meaning it communicates, and how to teach it. Prominence and tune both are primarily categorical in nature, while pitch range is primarily a gradient. Categorical meaning is the kind that native speakers largely will agree on, such as the difference between questions and statements, and gradient differences reflect varied and subjective perceptions of meaning, such as emotions or attitudes. Intonation is rarely the cause of word unintelligibility because intonation is not right or wrong in the way that segmentals and word stress are. Instead, intonation is important in other types of misunderstanding such as difficulties with comprehensibility, comprehension of the content of speech, or understanding the intent of an utterance. Thus, the misunderstandings that are related to misuse of intonation are often not immediately evident. This chapter addresses how intonation is related to intelligibility in English. It looks primarily at the impact of prominence (i.e., sentence or nuclear stress) and the influence of tune (i.e., intonation contours) on intelligibility.