Turner’s syndrome is a sporadic disorder of human females in which all or part of one X chromosome is deleted(1). Intelligence is usually normal(2) but social adjustment problems are common(3). Here we report a study of 80 females with Turner’s syndrome and a single X chromosome, in 55 of which the X was maternally derived (45,X-m) and in 25 it was of paternal origin (45,X-p). Members of the 45,XP group were significantly better adjusted, with superior verbal and higher-order executive function skills, which mediate social interactions(4). Our observations suggest that there is a genetic locus for social cognition, which is imprinted(5) and is not expressed from the maternally derived X chromosome. Neuropsychological and molecular investigations of eight females with partial deletions of the short arm of the X chromosome(6) indicate that the putative imprinted locus escapes inactivation(7), and probably lies on Xq or close to the centromere on Xp. If expressed only from the X chromosome of paternal origin, the existence of this locus could explain why 46,XY males (whose single X chromosome is maternal) are more vulnerable to developmental disorders of language and social cognition, such as autism, than are 46,XX females(8).