Introduction: A dysfunction of the process that leads to maturation of corpus callosum can determine an anomalous interhemispheric interaction and so justify the appearance of cognitive disorders. The present study attempted to investigate the possible relationship between the function of the corpus callosum and intellectual disability in subjects with Down’s Syndrome. Materials and methods: Four groups of subjects were examined: eleven individuals with Down’s Syndrome, eleven individuals with intellectual disability not due to genetic abnormality, thirteen healthy individuals matched on the basis of chronological age, and thirteen healthy individuals matched on the basis of the degree of intellectual level. A fingertip cross-localization task has been used to measure the efficiency of the interhemispheric transfer of information: since transferring tactile information from one hemisphere to the other implies a significant loss of accuracy, the degree of difference between the uni-hemispheric and bi-hemispheric conditions of the finger localization task is considered an adequate measure of the functional efficiency of the transfer processes trough the corpus callosum. Results: Subjects with Down’s syndrome show a significantly lower performance than all other participants: their loss of accuracy corresponds to 42.9%, whereas in healthy adult controls, it is 3.7%, in healthy children, it is 17.8% and in individuals with intellectual disability not due to genetic abnormalities, it is 33.3%. Conclusion: Individuals with Down’s syndrome present a severe deficit of interhemispheric communication. The possibility is discussed that this disconnection syndrome may play a role in the genesis of cognitive disorders and intellectual disabilities.