This paper reports the pitch range and vowel duration data from a group of children with Williams syndrome (WS) in comparison with a group of typically developing children matched for chronological age (CA) and a group matched for receptive language abilities (LA). It is found that the speech of the WS group has a greater pitch range than the typically developing children, and that that vowel duration in the WS groups tends to be more similar to the LA group. These findings are in line with the impressionistic results reported by Reilly, Klima and Bellugi [16], indicating that children with WS use affective prosody differently to typically developing children.