Syllable fusion is a Hong Kong Cantonese connected speech process, whereby edges of syllables are obscured by consonant lenition or deletion, and vowel reduction. More extreme fusion can simplify contour tones and merge the qualities of vowels that would be separated by an onset or coda consonant at more normal degrees of disjuncture between words. This paper investigates the influence of speech rate on syllable fusion. An experiment tested the prediction that faster speech rate would give rise to more occurrences of fusion forms and a greater degree of fusion. Subjects repeated word groups in two conditions: at normal rate and at fastest possible speech rates. Results show that speech rate is a reliable predictor for the amount and for the degree of fusion. Implications for incorporating prosody in speech synthesis systems are discussed.