Initial auxology, endocrine testing, and neurocognitive evaluation will be performed at our Center. Auxologic and neurocognitive testing will be repeated after 18 months of therapy at our Center. These studies are done at our Center to assure consistency of evaluation, which is a particular concern for the neurocognitive tests. Many of the children will also participate in other studies in our Center (MRI imaging, psychological evaluations of family function) that are not part of this application. Children begun on GH treatment will need to be seen by a pediatric endocrinologist for dosage adjustment after 3, 6, 9 and 12 months. The untreated children will also need to be seen by a pediatric endocrinologist for auxologic studies at the same time points. We enrolled 20 children in this study. Few of the children are located in any single geographic area; therefore, we will have 12-20 centers seeing individual children. Rather than developing new forms, standard NCGS intake forms will be used for the intermediate visits by the local pediatric endocrinologists.