Comparisons between children with Williams syndrome and control group children matched for age, sex, social class, and verbal intelligence provide support for a cognitive and behavioural phenotype in Williams syndrome. Children with the syndrome showed higher rates of behavioural and emotional difficulties when compared with the control group children, particularly in terms of concentration difficulties, excessive anxiety, and poor relationships with peers; and they also had significantly poorer visuo-spatial and motor skills. However, the Williams syndrome children were not uniformly poor in all areas of nonverbal abilities. Their visual recall skills were as good as those of the control group children, and their performance was superior to that of the control group children on a task of face recognition and on tasks requiring recall of verbal material.