Publisher Summary The corpus callosum is the major structure of the human brain that connects the two cerebral hemispheres. It is a broadband of more than 200 million nerve fibers that provide the main route for transfer and integration of information between the two hemispheres. The chapter discusses that studies of brain lateralization suggest each hemisphere of the brain performs specialized functions. Many individuals with agenesis of the corpus callosum (ACC) exhibit developmental delays and have other concurrent conditions. The therapeutic and service needs of each individual change over time and vary from person to person. Depending on the person, the delays or abnormalities are observed in areas such as behavior, cognition, speech/language, social, or motor development and involve difficulties with daily living and school. The corpus callosum provides the means for integrating the information from each hemisphere to perceive, comprehend, and act fully upon sensory input. Although there are other smaller commissures in the brain, those are comprised of significantly fewer nerve fibers than the corpus callosum. Thus, absence of the corpus callosum is considered a major brain anomaly.