Abstract
The aim of this article is to provide an in-depth description of the behavioral phenotype of Williams syndrome in a preschool-aged child. Williams syndrome is a neurodevelopmental, multisystem genetic disorder associated with mental retardation that predisposes individuals to a characteristic pattern of strengths and weaknesses in neuropsychological functioning. While much is known about functioning in adults, very few descriptions of early development are available in the literature. Implications for designing early intervention programs for children with this debilitating disorder are discussed.