This article investigates the perceptual effect of a high plateau in the intonation contour. Plateaux are flat stretches of contour and have been observed associated with high tones in Standard Southern British (SSB) English. The hypothesis that plateaux may make the accents with which they are associated sound higher in pitch than sharp peaks of the same maximum frequency is tested experimentally. In the first experiment listeners heard pairs of resynthesized utterances where the nuclear accent differed only in shape, not frequency. They indicated which stimulus they thought contained the higher pitched accent. Results showed that plateau-shaped accents sound higher than peaks. In the second experiment the effect of a plateau on prominence relations within an utterance is investigated. Listeners heard resynthesized sentences, and compared two accents. One group indicated which accent sounded higher in pitch and the other indicated which sounded more prominent. Results again indicated that plateau-shaped accents sound higher in pitch and also more prominent; judgments of pitch and prominence were very similar to one another. The results from both experiments indicated that accent shape is a perceptually important variable, although such a fine level of detail is not taken into account by autosegmental-metrical theories of intonation. (Contains 7 figures.)