We report evidence for relatively preserved musical rhythm processing in individuals with Williams syndrome, supporting the theory that musical ability constitutes an independent intelligence. Williams syndrome occurs in 1 out of 20,000 births and is associated with a defect in elastin production, impaired cognitive function, and poor spatial, quantitative, and reasoning abilities, coupled with excellent face processing and relatively strong language abilities in adolescents and adults. Previously, informal qualitative observations have revealed an unusual degree of musicality and engagement with musical stimuli in many individuals with Williams syndrome. In the present study, rhythm production was assessed for eight subjects with Williams syndrome and eight subjects in a comparison group by using an echo clapping task. Despite serious deficits in other cognitive domains and generally poor coordination, the subjects with Williams syndrome achieved accuracy scores equivalent to those of subjects in the comparison group and demonstrated equivalent abilities in meter change and beat maintenance. Most interestingly, when the subjects with Williams syndrome made errors in rhythm production, their errors were far more likely than comparison subjects' errors to form rhythmically compatible musical elaborations to the test items; that is, responses of subjects with Williams syndrome, when incorrect, tended to be creative extensions of the reference rhythm.