This paper reports the results of a study of the intonation of 18 Mandarin Chinese speakers lecturing in English. As a basis for the study, it is proposed that intonation be considered a grammar of cohesion in English discourse: Drawing from the intonational model of Pierrehumbert and Hirschberg (1990), it is argued that discrete morphemes of intonation correspond to the categories of cohesion in Halliday and Hasan's (1976) typology. The study investigated the hypothesis that the nonnative speakers who were able to use the intonation system of English most effectively would score higher on a global language test. Using a Computerized Speech Lab to measure pitch, four aspects of intonation were averaged for each speaker: (a) the pitch difference between newly introduced content words and function words, (b) the use of high pitch at phrase boundaries to link related constituents, (c) the use of pitch to distinguish contrasting items from given items, and (d) the paratone or increase in pitch range at rhetorical junctures to signal topic shift. These four measures were chosen for their contribution to the cohesion of the lectures. Multiple regression analysis indicates that the fourth intonation variable, the paratone, was a significant predictor of these subjects' English test scores. Examples are given of the other variables in context from both low- and high-scoring speakers. It is emphasized that intonation is not only a stylistic component of accent but also a meaning-bearing grammatical system.