Semantic-difference scores, as obtained in 2 auditory experiments in which native speakers of English were asked to estimate the semantic contrast in paired nuclear tones, were correlated with 2 sets of theoretical differences, as predicted by 2 theories of the structure of English intonation (J. B. Pierrehumbert [P], 1980 and C. Gussenhoven [G], 1983). The G theory was a better predictor of both sets of experimental scores. Not all component elements in the theories correlated significantly with the experimental scores. In theory P, only the element represented by the phrase accent appeared to account for some of the variation, while in G, the main predictors were pitch range and tone modifications.