The neurodevelopmental assessment in the NDC for Young Children is a unique service for children with neurogenetic disorders and related developmental problems. This assessment evaluates the learning style of the child and how it is related to the specific genetic disorder as well as to the child’s chronological age and his/her need for specialized services and possibly specialized schooling. It is a comprehensive assessment, which evaluates the following four areas of development and the unique learning style and developmental achievement of this child: a) Neuromotor: upper and lower extremity function b) Neurocognitive: learning and cognitive skills c) Speech and language: receptive, expressive, and oral-motor skills d) Neurobehavioral: attention, organization, activity and control. The primary purpose of this testing is to facilitate the overall care of the child with developmental disabilities. This testing evaluates the integrity of the child’s central nervous system and the relationship between brain and behavior with learning and developmental achievement. With the information obtained from testing, case management, coordination and appropriate triage of therapeutic services can be recommended in light of the child’s genetic disorder. This level of comprehensive testing often prevents further costs for individual evaluations for physical, occupational and speech therapists. The uniqueness of our assessment is the combination of the specialty training of the assessor and the compilation of 15 years of expertise in the neurobehavioral and neurodevelopmental problems of children with neurogenetic disorders. In the last three years, ninety children with sex chromosome variations, including seventy children with XXY, have been evaluated. This is one of the largest populations of children identified through prenatal diagnosis in the world. Boys with XXY may be at increased risk for behavioral problems and significant emotional difficulties if the speech, language and motor problems are not addressed as soon as possible. Specific recommendations are made regarding implementation of early intervention services in the community, necessary tests, and parental support. The testing is premised on the belief that each genetic disorder has a characteristic neurobehavioral profile. By understanding the profile, the appropriate services are implemented at the optimum time and for an adequate length of time. This is a cost-efficient approach to the child with developmental disabilities.