The paper reports on changes in IQ scores and in reading, spelling and arithmetic skills over time in 23 young adults with Williams syndrome. They were first assessed in their early to mid-teens and followed up 8 to 9 years later, at an average age of 21 years 9 months. Cognitive assessments indicated increases in Full Scale, Verbal and Performance IQ scores. These increases allow us to conclude that in the case of Williams syndrome (unlike some other conditions) there does not appear to be a decline in the rate of cognitive development over time. Comparisons of Reading, Spelling and Arithmetic scores attained at first and second testing periods revealed only modest increases in reading accuracy and spelling scores, a slight decline in reading comprehension scores, and little change in arithmetic test scores. Differences in the tests used at the two assessment periods do not allow for definitive conclusions to be drawn, but the findings suggest that individuals with Williams syndrome make little progress in their educational skills beyond their early teenage years.